diff --git a/autoloader/index/0.php b/autoloader/index/0.php
index e7b8cf5..47ec1ed 100644
--- a/autoloader/index/0.php
+++ b/autoloader/index/0.php
@@ -171,6 +171,8 @@
     'malkusch\bav\validatord9' => '../classes/validator/validators/ValidatorD9.php',
     'malkusch\bav\validatore0' => '../classes/validator/validators/ValidatorE0.php',
     'malkusch\bav\validatore1' => '../classes/validator/validators/ValidatorE1.php',
+    'malkusch\bav\validatore2' => '../classes/validator/validators/ValidatorE2.php',
+    'malkusch\bav\validatore3' => '../classes/validator/validators/ValidatorE3.php',
     'malkusch\bav\domuripicker' => '../classes/dataBackend/file/download/uripicker/DOMURIPicker.php',
     'malkusch\bav\bavexception' => '../classes/exception/BAVException.php',
     'malkusch\bav\validator51x' => '../classes/validator/validators/Validator51x.php',
diff --git a/classes/BAV.php b/classes/BAV.php
index d52e63f..916b5c6 100644
--- a/classes/BAV.php
+++ b/classes/BAV.php
@@ -29,7 +29,7 @@ class BAV
      * @var DataBackend
      */
     private $backend;
-    
+
     /**
      * @var ContextValidation
      */
@@ -43,7 +43,7 @@ class BAV
      *
      * @see ConfigurationRegistry
      */
-    public function __construct(Configuration $configuration = null)
+    public function __construct(?Configuration $configuration = null)
     {
         if (is_null($configuration)) {
             $configuration = ConfigurationRegistry::getConfiguration();
@@ -52,7 +52,7 @@ public function __construct(Configuration $configuration = null)
         $this->configuration = $configuration;
 
         $this->backend = $configuration->getDataBackendContainer()->getDataBackend();
-        
+
         $this->contextValidation = new ContextValidation($this->backend);
     }
 
@@ -133,7 +133,7 @@ public function isValidBank($bankID)
     {
         return $this->contextValidation->isValidBank($bankID);
     }
-    
+
     /**
      * Every bank has one main agency.
      *
@@ -165,7 +165,7 @@ public function getAgencies($bankID)
     {
         return $this->getBank($bankID)->getAgencies();
     }
-    
+
     /**
      * With this method you get the Bank objects for certain IDs. Note
      * that a call to this method with an identical id will return the same
@@ -203,7 +203,7 @@ public function isValidBIC($bic)
     {
         return $this->backend->isValidBIC(BICUtil::normalize($bic));
     }
-    
+
     /**
      * Returns the third call back parameter for filter_var() for validating
      * a bank.
@@ -218,7 +218,7 @@ public function getValidBankFilterCallback()
     {
         return $this->contextValidation->getValidBankFilterCallback();
     }
-    
+
     /**
      * Returns the third call back parameter for filter_var() for validating
      * a bank account.
diff --git a/classes/configuration/Configuration.php b/classes/configuration/Configuration.php
index 6302367..c16e5f8 100644
--- a/classes/configuration/Configuration.php
+++ b/classes/configuration/Configuration.php
@@ -44,7 +44,7 @@ class Configuration
      *
      * Set to null if you don't want to use an update plan.
      */
-    public function setUpdatePlan(UpdatePlan $updatePlan = null)
+    public function setUpdatePlan(?UpdatePlan $updatePlan = null)
     {
         $this->updatePlan = $updatePlan;
     }
@@ -100,7 +100,7 @@ public function getDataBackendContainer()
     {
         return $this->backendContainer;
     }
-    
+
     /**
      * Sets the encoding.
      */
diff --git a/classes/dataBackend/file/FileDataBackend.php b/classes/dataBackend/file/FileDataBackend.php
index 4be6d60..b85894e 100644
--- a/classes/dataBackend/file/FileDataBackend.php
+++ b/classes/dataBackend/file/FileDataBackend.php
@@ -16,9 +16,12 @@
  */
 class FileDataBackend extends DataBackend
 {
-    
+
     // @codingStandardsIgnoreStart
-    const DOWNLOAD_URI = "http://www.bundesbank.de/Redaktion/DE/Standardartikel/Aufgaben/Unbarer_Zahlungsverkehr/bankleitzahlen_download.html";
+    // The parent contains something like this:
+    // https://www.bundesbank.de/resource/blob/602632/31fec41357f012d537ce62045395929a/mL/blz-aktuell-txt-data.txt
+    const DOWNLOAD_BASE_URI = "https://www.bundesbank.de";
+    const DOWNLOAD_PARENT_URI= self::DOWNLOAD_BASE_URI . "/de/aufgaben/unbarer-zahlungsverkehr/serviceangebot/bankleitzahlen/download-bankleitzahlen-602592";
     // @codingStandardsIgnoreEnd
 
     /**
@@ -30,7 +33,7 @@ class FileDataBackend extends DataBackend
      * @var FileParser
      */
     private $parser;
-    
+
     /**
      * @var Index_FixedSize
      */
@@ -49,7 +52,7 @@ public function __construct($file = null)
         $this->parser = new FileParser($file);
         $this->fileUtil = new FileUtil();
     }
-    
+
     /**
      * @return FixedSizeIndex
      */
@@ -61,7 +64,7 @@ private function getIndex()
                 FileParser::BANKID_OFFSET,
                 FileParser::BANKID_LENGTH
             );
-            
+
         }
         return $this->index;
     }
@@ -159,34 +162,19 @@ public function install()
     public function update()
     {
         $downloader = new Downloader();
-        $content = $downloader->downloadContent(self::DOWNLOAD_URI);
-
-        $uriPicker = new FallbackURIPicker();
-        $path = $uriPicker->pickURI($content);
-
-        if (strlen($path) > 0 && $path{0} != "/") {
-            $path = sprintf("/%s/%s", dirname(self::DOWNLOAD_URI), $path);
 
-        }
-        $pathParts = explode('/', $path);
-        foreach ($pathParts as $i => $part) {
-            switch ($part) {
-                case '..':
-                    unset($pathParts[$i-1]);
-                    // fall-through as the current part ("..") should be removed as well.
-
-                case '.':
-                    unset($pathParts[$i]);
-                    break;
+        $parentContent = $downloader->downloadContent(self::DOWNLOAD_PARENT_URI);
+        if (preg_match('|href="([^"]+/blz-aktuell-txt-data.txt)"|', $parentContent, $matches)) {
+            $downloadUri = $matches[1];
+            if (!str_starts_with($downloadUri, 'https://')) {
+                $downloadUri = self::DOWNLOAD_BASE_URI . $downloadUri;
             }
-
+        } else {
+            throw new DownloaderException("Failed opening parent page " . self::DOWNLOAD_PARENT_URI . " containing download-uri");
         }
-        $path = implode('/', $pathParts);
-        $urlParts = parse_url(self::DOWNLOAD_URI);
-        $url = sprintf("%s://%s%s", $urlParts["scheme"], $urlParts["host"], $path);
 
         // download file
-        $file = $downloader->downloadFile($url);
+        $file = $downloader->downloadFile($downloadUri);
 
         // Validate file format.
         $validator = new FileValidator();
@@ -245,7 +233,7 @@ public function getNewBank($bankID)
     {
         try {
             $result = $this->getIndex()->search($bankID);
-        
+
             if ($result == null) {
                 throw new BankNotFoundException($bankID);
 
@@ -261,7 +249,7 @@ public function getNewBank($bankID)
 
         } catch (IndexException $e) {
             throw new DataBackendIOException($e->getMessage(), $e->getCode(), $e);
-            
+
         }
     }
 
@@ -419,7 +407,7 @@ public function getBICAgencies($bic)
         }
         return $agencies;
     }
-    
+
     public function free()
     {
         parent::free();
diff --git a/classes/dataBackend/file/download/Downloader.php b/classes/dataBackend/file/download/Downloader.php
index 283c5e2..d9eeca7 100644
--- a/classes/dataBackend/file/download/Downloader.php
+++ b/classes/dataBackend/file/download/Downloader.php
@@ -25,7 +25,7 @@ class Downloader
     public function __construct()
     {
         $this->handle = curl_init();
-        if (! is_resource($this->handle)) {
+        if (! is_resource($this->handle) && !($this->handle instanceof \CurlHandle)) {
             throw new DownloaderException("Failed initializing curl");
 
         }
@@ -92,6 +92,7 @@ public function downloadFile($uri)
 
         }
         curl_setopt($this->handle, CURLOPT_FILE, $fp);
+        curl_setopt($this->handle, CURLOPT_FOLLOWLOCATION, 1);
 
         if (! $this->download($uri)) {
             fclose($fp);
diff --git a/classes/dataBackend/pdo/PDODataBackend.php b/classes/dataBackend/pdo/PDODataBackend.php
index 72bfb83..c2617be 100644
--- a/classes/dataBackend/pdo/PDODataBackend.php
+++ b/classes/dataBackend/pdo/PDODataBackend.php
@@ -524,7 +524,7 @@ public function getLastUpdate()
 
         } catch (\PDOException $e) {
             $stmt->closeCursor();
-            throw new DataBackendIOException($e->getMessage(), $e->getCode(), $e);
+            throw new DataBackendIOException($e->getMessage(), (int)$e->getCode(), $e);
 
         }
     }
@@ -538,37 +538,15 @@ public function getLastUpdate()
     public function isInstalled()
     {
         try {
-            switch ($this->pdo->getAttribute(\PDO::ATTR_DRIVER_NAME)) {
-                case "sqlite":
-                    $query =
-                        "SELECT count(*) FROM sqlite_master
-                            WHERE type='table' AND name = '{$this->prefix}meta'";
-                    break;
-                
-                default:
-                    $query =
-                        "SELECT CASE WHEN EXISTS(
-                            (SELECT * FROM information_schema.tables
-                                WHERE table_name='{$this->prefix}meta')
-                        ) THEN 1 ELSE 0 END";
-                    break;
-                
-            }
-            
+            $query = "SELECT COUNT(*) FROM {$this->prefix}meta";
             $stmt = $this->statementContainer->prepare($query);
             $stmt->execute();
             $result = $stmt->fetch();
-            if ($result === false) {
-                throw new DataBackendException();
-
-            }
             $stmt->closeCursor();
-            return $result[0] == 1;
-
+            return !($result === false);
         } catch (\PDOException $e) {
             $stmt->closeCursor();
-            throw new DataBackendIOException($e->getMessage(), 0, $e);
-
+            return false;
         }
     }
 
diff --git a/classes/validator/Validator.php b/classes/validator/Validator.php
index a7ea34c..4f088c6 100644
--- a/classes/validator/Validator.php
+++ b/classes/validator/Validator.php
@@ -74,7 +74,7 @@ protected function checkType($account)
     {
         if (is_string($account)) {
             return;
-            
+
         }
         trigger_error(
             "Only validation of strings are defined."
@@ -82,7 +82,7 @@ protected function checkType($account)
             E_USER_WARNING
         );
     }
-    
+
     /**
      * Validates a bank account.
      *
@@ -101,7 +101,7 @@ public function isValid($account)
         try {
             if ($account == null) {
                 return false;
-                
+
             }
             $this->checkType($account);
             $this->init($account);
@@ -148,7 +148,7 @@ abstract protected function getResult();
      */
     protected function getChecknumber()
     {
-        return $this->account{$this->getNormalizedPosition($this->checknumberPosition)};
+        return $this->account[$this->getNormalizedPosition($this->checknumberPosition)];
     }
 
     /**
@@ -184,7 +184,7 @@ protected function crossSum($int)
         $str_int = (string) $int;
         for ($i = 0; $i < strlen($str_int); $i++) {
             //$sum = bcadd($str_int{$i}, $sum);
-            $sum += $str_int{$i};
+            $sum += $str_int[$i];
 
         }
         return $sum;
@@ -217,7 +217,7 @@ protected function getESER8()
 
         }
         $bankID = $this->bank->getBankID();
-        if ($bankID{3} != 5) {
+        if ($bankID[3] != 5) {
             throw new ValidatorESERException();
 
         }
@@ -230,7 +230,7 @@ protected function getESER8()
 
         }
         $accountPart = ltrim(substr($account, 2), '0');
-        $eser        = $blzPart.$account{0}.$account{1}.$accountPart;
+        $eser        = $blzPart.$account[0].$account[1].$accountPart;
 
         return $eser;
     }
@@ -249,7 +249,7 @@ protected function getESER9()
             throw new ValidatorESERException();
 
         }
-        if ($bankID{3} != 5) {
+        if ($bankID[3] != 5) {
             throw new ValidatorESERException();
 
         }
@@ -257,9 +257,9 @@ protected function getESER9()
         $blzPart0 = substr($bankID, -4, 2);
         $blzPart1 = substr($bankID, -1);
 
-        $accountPart0 = $account{0};
-        $t            = $account{1};
-        $p            = $account{2};
+        $accountPart0 = $account[0];
+        $t            = $account[1];
+        $p            = $account[2];
         $accountTail  = ltrim(substr($account, 3), '0');
 
         $eser = $blzPart0.$t.$blzPart1.$accountPart0.$p.$accountTail;
@@ -273,7 +273,7 @@ protected function getEserChecknumberPosition()
 
     protected function getEserChecknumber()
     {
-        return $this->account{$this->getEserChecknumberPosition()};
+        return $this->account[$this->getEserChecknumberPosition()];
     }
 
     protected function isBetween($a, $b)
diff --git a/classes/validator/ValidatorIteration.php b/classes/validator/ValidatorIteration.php
index 20832d2..ee069a5 100644
--- a/classes/validator/ValidatorIteration.php
+++ b/classes/validator/ValidatorIteration.php
@@ -104,7 +104,7 @@ protected function validate()
 
 
         for ($this->i = 0; $this->i < $length; $this->i++) {
-            $this->number = (int)$this->account{$this->position};
+            $this->number = (int)$this->account[$this->position];
             $this->iterationStep();
             $this->position += $stepping;
 
diff --git a/classes/validator/validators/Validator16.php b/classes/validator/validators/Validator16.php
index e7b47e3..3a8d551 100644
--- a/classes/validator/validators/Validator16.php
+++ b/classes/validator/validators/Validator16.php
@@ -34,7 +34,7 @@ public function __construct(Bank $bank)
     protected function getResult()
     {
          return $this->accumulator % 11 === 1
-              ? $this->getChecknumber() === $this->account{$this->getNormalizedPosition($this->checknumberPosition) - 1}
+              ? $this->getChecknumber() === $this->account[$this->getNormalizedPosition($this->checknumberPosition) - 1]
               : parent::getResult();
     }
 }
diff --git a/classes/validator/validators/Validator25.php b/classes/validator/validators/Validator25.php
index 6e9bbc7..bf74dd7 100644
--- a/classes/validator/validators/Validator25.php
+++ b/classes/validator/validators/Validator25.php
@@ -40,9 +40,10 @@ protected function getResult()
     {
         $result = 11 - ($this->accumulator % 11);
         switch ($result) {
+
             case 10:
                 $result = 0;
-                if ($this->account{1} != 8 && $this->account{1} != 9) {
+                if ($this->account[1] != 8 && $this->account[1] != 9) {
                     return false;
 
                 }
diff --git a/classes/validator/validators/Validator35.php b/classes/validator/validators/Validator35.php
index 261dd3e..c2185e6 100644
--- a/classes/validator/validators/Validator35.php
+++ b/classes/validator/validators/Validator35.php
@@ -40,7 +40,7 @@ protected function getResult()
     {
         $result = $this->accumulator % 11;
         if ($result === 10) {
-            return $this->account{9} === $this->account{8};
+            return $this->account[9] === $this->account[8];
 
         }
         return (string)$result === $this->getCheckNumber();
diff --git a/classes/validator/validators/Validator41.php b/classes/validator/validators/Validator41.php
index 728330e..ad03dec 100644
--- a/classes/validator/validators/Validator41.php
+++ b/classes/validator/validators/Validator41.php
@@ -35,7 +35,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        if ($this->account{3} == 9) {
+        if ($this->account[3] == 9) {
             $this->setEnd(3);
 
         } else {
diff --git a/classes/validator/validators/Validator45.php b/classes/validator/validators/Validator45.php
index faf778a..0bf4bed 100644
--- a/classes/validator/validators/Validator45.php
+++ b/classes/validator/validators/Validator45.php
@@ -36,8 +36,8 @@ public function __construct(Bank $bank)
      */
     protected function getResult()
     {
-        return $this->account{0} === '0'
-            || $this->account{4} === '1'
+        return $this->account[0] === '0'
+            || $this->account[4] === '1'
             || parent::getResult();
     }
 }
diff --git a/classes/validator/validators/Validator51.php b/classes/validator/validators/Validator51.php
index 3f0e2a9..14d7dc6 100644
--- a/classes/validator/validators/Validator51.php
+++ b/classes/validator/validators/Validator51.php
@@ -93,7 +93,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? $this->exceptionValidators
                           : $this->defaultValidators;
     }
@@ -104,7 +104,7 @@ protected function continueValidation(Validator $validator)
             return true;
 
         }
-        switch ($this->account{9}) {
+        switch ($this->account[9]) {
             case 7:
             case 8:
             case 9:
diff --git a/classes/validator/validators/Validator52.php b/classes/validator/validators/Validator52.php
index 346ed29..ca552f5 100644
--- a/classes/validator/validators/Validator52.php
+++ b/classes/validator/validators/Validator52.php
@@ -49,7 +49,7 @@ public function __construct(Bank $bank)
     public function isValid($account)
     {
         try {
-            return strlen($account) == 10 && $account{0} == 9
+            return strlen($account) == 10 && $account[0] == 9
                  ? $this->validator20->isValid($account)
                  : parent::isValid($account);
 
diff --git a/classes/validator/validators/Validator56.php b/classes/validator/validators/Validator56.php
index a6a1a99..654bd77 100644
--- a/classes/validator/validators/Validator56.php
+++ b/classes/validator/validators/Validator56.php
@@ -39,7 +39,7 @@ protected function iterationStep()
     protected function getResult()
     {
         $result = 11 - ($this->accumulator % 11);
-        if ($this->account{0} == 9 && $result >= 10) {
+        if ($this->account[0] == 9 && $result >= 10) {
             $result -= 3;
 
         }
diff --git a/classes/validator/validators/Validator61.php b/classes/validator/validators/Validator61.php
index ffe562c..c9f4322 100644
--- a/classes/validator/validators/Validator61.php
+++ b/classes/validator/validators/Validator61.php
@@ -37,7 +37,7 @@ public function init($account)
         parent::init($account);
 
 
-        if ($this->account{8} == 8) {
+        if ($this->account[8] == 8) {
             $this->setWeights(array(2, 1, 2, 1, 2, 1, 2, 0, 1, 2));
             $this->setEnd(-1);
 
diff --git a/classes/validator/validators/Validator63.php b/classes/validator/validators/Validator63.php
index 2900ef5..c916b9a 100644
--- a/classes/validator/validators/Validator63.php
+++ b/classes/validator/validators/Validator63.php
@@ -55,6 +55,6 @@ protected function iterationStep()
     protected function getResult()
     {
         $result = (10 - ($this->accumulator % 10)) % 10;
-        return $this->account{0} == '0' && (string)$result === $this->getCheckNumber();
+        return $this->account[0] == '0' && (string)$result === $this->getCheckNumber();
     }
 }
diff --git a/classes/validator/validators/Validator65.php b/classes/validator/validators/Validator65.php
index 14c1024..8080e97 100644
--- a/classes/validator/validators/Validator65.php
+++ b/classes/validator/validators/Validator65.php
@@ -37,7 +37,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        if ($this->account{8} == 9) {
+        if ($this->account[8] == 9) {
             $this->setEnd(-1);
 
         } else {
diff --git a/classes/validator/validators/Validator66.php b/classes/validator/validators/Validator66.php
index 742d27f..91054bf 100644
--- a/classes/validator/validators/Validator66.php
+++ b/classes/validator/validators/Validator66.php
@@ -41,11 +41,11 @@ protected function iterationStep()
     protected function getResult()
     {
         // update 2014-03-03
-        if ($this->account{1} == '9') {
+        if ($this->account[1] == '9') {
             return true;
 
         }
         $result = (11 - $this->accumulator % 11) % 10;
-        return $this->account{0} == '0' && (string)$result === $this->getCheckNumber();
+        return $this->account[0] == '0' && (string)$result === $this->getCheckNumber();
     }
 }
diff --git a/classes/validator/validators/Validator68.php b/classes/validator/validators/Validator68.php
index 05245d5..18e56cd 100644
--- a/classes/validator/validators/Validator68.php
+++ b/classes/validator/validators/Validator68.php
@@ -60,8 +60,9 @@ protected function init($account)
     protected function getResult()
     {
         switch (strlen($this->account)) {
+
             case 10:
-                return $this->account{3} == 9 && $this->validator10->isValid($this->account);
+                return $this->account[3] == 9 && $this->validator10->isValid($this->account);
 
             case 9:
                 if ($this->account >= 400000000 && $this->account <= 499999999) {
diff --git a/classes/validator/validators/Validator70.php b/classes/validator/validators/Validator70.php
index b55d4fb..412ab28 100644
--- a/classes/validator/validators/Validator70.php
+++ b/classes/validator/validators/Validator70.php
@@ -33,7 +33,7 @@ public function __construct(Bank $bank)
 
     protected function iterationStep()
     {
-        if ($this->position <= 2 && ($this->account{3} == 5 || substr($this->account, 3, 2) == 69)) {
+        if ($this->position <= 2 && ($this->account[3] == 5 || substr($this->account, 3, 2) == 69)) {
             return;
 
         }
diff --git a/classes/validator/validators/Validator73.php b/classes/validator/validators/Validator73.php
index 82a46c4..e0306b3 100644
--- a/classes/validator/validators/Validator73.php
+++ b/classes/validator/validators/Validator73.php
@@ -59,7 +59,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        if ($this->account{2} == 9) {
+        if ($this->account[2] == 9) {
             $this->validators = $this->exceptionValidators;
 
         } else {
diff --git a/classes/validator/validators/Validator74.php b/classes/validator/validators/Validator74.php
index 2006d39..6b3d5d6 100644
--- a/classes/validator/validators/Validator74.php
+++ b/classes/validator/validators/Validator74.php
@@ -37,18 +37,30 @@ public function isValid($account)
     }
 
     protected function getResult()
+    {
+        return $this->variantOne() || $this->variantTwo();
+    }
+
+    private function variantOne()
     {
         if (parent::getResult()) {
             return true;
-
         } elseif (strlen(ltrim($this->account, '0')) == 6) {
-            $nextHalfDecade = round($this->accumulator/10) * 10 + 5;
-            $check          = ($nextHalfDecade - $this->accumulator) % 10;
-            return (string) $check === $this->getChecknumber();
-
-        } else {
-            return false;
+            $nextHalfDecade = round($this->accumulator / 10) * 10 + 5;
+            $check = ($nextHalfDecade - $this->accumulator) % 10;
 
+            return (string)$check === $this->getChecknumber();
         }
+
+        return false;
+    }
+
+    private function variantTwo()
+    {
+        $validator = new Validator04($this->bank);
+        $validator->setWeights([2, 3, 4, 5, 6, 7, 2, 3, 4]);
+        $validator->setDivisor(11);
+
+        return $validator->isValid($this->account);
     }
-}
+}
\ No newline at end of file
diff --git a/classes/validator/validators/Validator75.php b/classes/validator/validators/Validator75.php
index 1231341..fa27972 100644
--- a/classes/validator/validators/Validator75.php
+++ b/classes/validator/validators/Validator75.php
@@ -45,7 +45,7 @@ public function isValid($account)
 
         }
         if ($length == 9) {
-            if ($account{0} == 9) {
+            if ($account[0] == 9) {
                 $account = substr($account, 1, 6);
 
             } else {
diff --git a/classes/validator/validators/Validator76.php b/classes/validator/validators/Validator76.php
index 6f84846..f4d6801 100644
--- a/classes/validator/validators/Validator76.php
+++ b/classes/validator/validators/Validator76.php
@@ -57,7 +57,7 @@ protected function iterationStep()
     protected function getResult()
     {
         $result = $this->accumulator % 11;
-        return array_search((int)$this->account{0}, array(0, 4, 6, 7, 8, 9)) !== false
+        return array_search((int)$this->account[0], array(0, 4, 6, 7, 8, 9)) !== false
             && $result != 10
             && (string)$result === $this->getCheckNumber();
     }
diff --git a/classes/validator/validators/Validator79.php b/classes/validator/validators/Validator79.php
index 0931624..a3973a7 100644
--- a/classes/validator/validators/Validator79.php
+++ b/classes/validator/validators/Validator79.php
@@ -63,10 +63,10 @@ protected function init($account)
 
     protected function validate()
     {
-        if (array_search($this->account{0}, array(1, 2, 9)) !== false) {
+        if (array_search($this->account[0], array(1, 2, 9)) !== false) {
             $this->validator = $this->mode2;
 
-        } elseif ($this->account{0} == 0) {
+        } elseif ($this->account[0] == 0) {
             $this->validator = null;
 
         } else {
diff --git a/classes/validator/validators/Validator80.php b/classes/validator/validators/Validator80.php
index e852e93..16f4e7b 100644
--- a/classes/validator/validators/Validator80.php
+++ b/classes/validator/validators/Validator80.php
@@ -54,7 +54,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? $this->exceptionValidators
                           : $this->defaultValidators;
     }
diff --git a/classes/validator/validators/Validator81.php b/classes/validator/validators/Validator81.php
index fd4ae39..3e8663a 100644
--- a/classes/validator/validators/Validator81.php
+++ b/classes/validator/validators/Validator81.php
@@ -50,7 +50,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? $this->exceptionValidators
                           : $this->defaultValidators;
     }
diff --git a/classes/validator/validators/Validator83.php b/classes/validator/validators/Validator83.php
index 1fd435c..c76b387 100644
--- a/classes/validator/validators/Validator83.php
+++ b/classes/validator/validators/Validator83.php
@@ -73,6 +73,6 @@ protected function init($account)
 
     protected function continueValidation(Validator $validator)
     {
-        return $validator !== $this->modeC || $this->account{9} < 7;
+        return $validator !== $this->modeC || $this->account[9] < 7;
     }
 }
diff --git a/classes/validator/validators/Validator84.php b/classes/validator/validators/Validator84.php
index 4824949..f69c0c9 100644
--- a/classes/validator/validators/Validator84.php
+++ b/classes/validator/validators/Validator84.php
@@ -59,7 +59,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? $this->exceptionValidators
                           : $this->defaultValidators;
     }
diff --git a/classes/validator/validators/Validator85.php b/classes/validator/validators/Validator85.php
index 69b8d44..42f89a0 100644
--- a/classes/validator/validators/Validator85.php
+++ b/classes/validator/validators/Validator85.php
@@ -75,6 +75,6 @@ protected function init($account)
 
     protected function continueValidation(Validator $validator)
     {
-        return $validator !== $this->modeC || $this->account{9} < 7;
+        return $validator !== $this->modeC || $this->account[9] < 7;
     }
 }
diff --git a/classes/validator/validators/Validator86.php b/classes/validator/validators/Validator86.php
index 082518b..a6ef028 100644
--- a/classes/validator/validators/Validator86.php
+++ b/classes/validator/validators/Validator86.php
@@ -55,7 +55,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? $this->exceptionValidators
                           : $this->defaultValidators;
     }
diff --git a/classes/validator/validators/Validator87.php b/classes/validator/validators/Validator87.php
index 48dcff8..3cbd8a0 100644
--- a/classes/validator/validators/Validator87.php
+++ b/classes/validator/validators/Validator87.php
@@ -59,7 +59,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? $this->exceptionValidators
                           : $this->defaultValidators;
     }
diff --git a/classes/validator/validators/Validator87a.php b/classes/validator/validators/Validator87a.php
index 1790aab..4b77ce3 100644
--- a/classes/validator/validators/Validator87a.php
+++ b/classes/validator/validators/Validator87a.php
@@ -40,7 +40,6 @@ protected function validate()
      */
     protected function getResult()
     {
-        $accountID = $this->account;
         $i      = 0;
         $c2     = 0;
         $d2     = 0;
@@ -50,8 +49,8 @@ protected function getResult()
         $tab2   = array(7, 1, 5, 9, 8);
         $konto  = array();
 
-        for ($i = 0; $i < strlen($accountID); $i++) {
-            $konto[$i+1] = $accountID{$i};
+        for ($i = 0; $i < strlen($this->account); $i++) {
+            $konto[$i+1] = $this->account[$i];
         }
 
         $i = 4;
@@ -63,17 +62,13 @@ protected function getResult()
 
         while ($i < 10) {
             switch ($konto[$i]) {
-                case 0:
-                    $konto[$i] = 5;
+                case 0: $konto[$i] = 5;
                     break;
-                case 1:
-                    $konto[$i] = 6;
+                case 1: $konto[$i] = 6;
                     break;
-                case 5:
-                    $konto[$i] = 10;
+                case 5: $konto[$i] = 10;
                     break;
-                case 6:
-                    $konto[$i] = 1;
+                case 6: $konto[$i] = 1;
                     break;
             }
 
diff --git a/classes/validator/validators/Validator88.php b/classes/validator/validators/Validator88.php
index 19f4bc3..180bd38 100644
--- a/classes/validator/validators/Validator88.php
+++ b/classes/validator/validators/Validator88.php
@@ -36,6 +36,6 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->setEnd($this->account{2} == 9 ? 2: 3);
+        $this->setEnd($this->account[2] == 9 ? 2: 3);
     }
 }
diff --git a/classes/validator/validators/Validator90.php b/classes/validator/validators/Validator90.php
index 5ca298c..e10c46b 100644
--- a/classes/validator/validators/Validator90.php
+++ b/classes/validator/validators/Validator90.php
@@ -63,7 +63,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? array($this->modeF)
                           : $this->defaultValidators;
     }
diff --git a/classes/validator/validators/Validator90c.php b/classes/validator/validators/Validator90c.php
index c39acbe..a9f6f7d 100644
--- a/classes/validator/validators/Validator90c.php
+++ b/classes/validator/validators/Validator90c.php
@@ -43,6 +43,6 @@ protected function getResult()
         $result = $result == 7
                 ? 0
                 : $result % 10;
-        return $this->account{9} < 7 && (string)$result === $this->getCheckNumber();
+        return $this->account[9] < 7 && (string)$result === $this->getCheckNumber();
     }
 }
diff --git a/classes/validator/validators/Validator90d.php b/classes/validator/validators/Validator90d.php
index 3d6227a..f1868eb 100644
--- a/classes/validator/validators/Validator90d.php
+++ b/classes/validator/validators/Validator90d.php
@@ -43,6 +43,6 @@ protected function getResult()
         $result = $result == 9
                 ? 0
                 : $result % 10;
-        return $this->account{9} != 9 && (string)$result === $this->getCheckNumber();
+        return $this->account[9] != 9 && (string)$result === $this->getCheckNumber();
     }
 }
diff --git a/classes/validator/validators/ValidatorA5.php b/classes/validator/validators/ValidatorA5.php
index 7e71356..4ee2e28 100644
--- a/classes/validator/validators/ValidatorA5.php
+++ b/classes/validator/validators/ValidatorA5.php
@@ -38,7 +38,7 @@ public function __construct(Bank $bank)
     protected function continueValidation(Validator $validator)
     {
         if ($validator === $this->validators[1]) {
-            return $this->account{0} !== '9';
+            return $this->account[0] !== '9';
 
         }
         return true;
diff --git a/classes/validator/validators/ValidatorA6.php b/classes/validator/validators/ValidatorA6.php
index e33d914..7e0195a 100644
--- a/classes/validator/validators/ValidatorA6.php
+++ b/classes/validator/validators/ValidatorA6.php
@@ -57,7 +57,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = $this->account{1} === '8'
+        $this->validator = $this->account[1] === '8'
                          ? $this->mode1
                          : $this->mode2;
     }
diff --git a/classes/validator/validators/ValidatorA8.php b/classes/validator/validators/ValidatorA8.php
index 815303f..c4b9721 100644
--- a/classes/validator/validators/ValidatorA8.php
+++ b/classes/validator/validators/ValidatorA8.php
@@ -63,7 +63,7 @@ protected function init($account)
     {
         parent::init($account);
 
-        $this->validators = $this->account{2} == 9
+        $this->validators = $this->account[2] == 9
                           ? $this->exceptionValidators
                           : $this->defaultValidators;
     }
diff --git a/classes/validator/validators/ValidatorB0.php b/classes/validator/validators/ValidatorB0.php
index 03aad10..5104b62 100644
--- a/classes/validator/validators/ValidatorB0.php
+++ b/classes/validator/validators/ValidatorB0.php
@@ -56,7 +56,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = array_search($this->account{7}, array(1, 2, 3, 6)) !== false
+        $this->validator = array_search($this->account[7], array(1, 2, 3, 6)) !== false
                          ? $this->mode1
                          : $this->mode2;
     }
@@ -67,7 +67,7 @@ protected function validate()
     protected function getResult()
     {
         return strlen(ltrim($this->account, '0')) === 10
-            && $this->account{0} !== '8'
+            && $this->account[0] !== '8'
             && $this->validator->isValid($this->account);
     }
 }
diff --git a/classes/validator/validators/ValidatorB1.php b/classes/validator/validators/ValidatorB1.php
index f9d4f05..27246c9 100644
--- a/classes/validator/validators/ValidatorB1.php
+++ b/classes/validator/validators/ValidatorB1.php
@@ -29,9 +29,7 @@ public function __construct(Bank $bank)
         parent::__construct($bank);
 
         $this->validators[] = new Validator05($bank);
-        $this->validators[0]->setWeights(array(7, 3, 1));
-
         $this->validators[] = new Validator01($bank);
-        $this->validators[1]->setWeights(array(3, 7, 1));
+        $this->validators[] = new Validator00($bank);
     }
-}
+}
\ No newline at end of file
diff --git a/classes/validator/validators/ValidatorB2.php b/classes/validator/validators/ValidatorB2.php
index f81deee..8a6d2af 100644
--- a/classes/validator/validators/ValidatorB2.php
+++ b/classes/validator/validators/ValidatorB2.php
@@ -57,7 +57,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = $this->account{0} <= 7
+        $this->validator = $this->account[0] <= 7
                          ? $this->mode1
                          : $this->mode2;
     }
diff --git a/classes/validator/validators/ValidatorB3.php b/classes/validator/validators/ValidatorB3.php
index 36fe3c8..2ddfacd 100644
--- a/classes/validator/validators/ValidatorB3.php
+++ b/classes/validator/validators/ValidatorB3.php
@@ -57,7 +57,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = $this->account{0} != 9
+        $this->validator = $this->account[0] != 9
                          ? $this->mode1
                          : $this->mode2;
     }
diff --git a/classes/validator/validators/ValidatorB4.php b/classes/validator/validators/ValidatorB4.php
index ac2418f..fed53cd 100644
--- a/classes/validator/validators/ValidatorB4.php
+++ b/classes/validator/validators/ValidatorB4.php
@@ -57,7 +57,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = $this->account{0} == 9
+        $this->validator = $this->account[0] == 9
                          ? $this->mode1
                          : $this->mode2;
     }
diff --git a/classes/validator/validators/ValidatorB5.php b/classes/validator/validators/ValidatorB5.php
index cc6c4e4..1f56eca 100644
--- a/classes/validator/validators/ValidatorB5.php
+++ b/classes/validator/validators/ValidatorB5.php
@@ -41,7 +41,7 @@ public function __construct(Bank $bank)
     protected function continueValidation(Validator $validator)
     {
         if ($validator === $this->validators[1]) {
-            return $this->account{0} < 8;
+            return $this->account[0] < 8;
 
         }
         return true;
diff --git a/classes/validator/validators/ValidatorB6.php b/classes/validator/validators/ValidatorB6.php
index 025cc55..84554f6 100644
--- a/classes/validator/validators/ValidatorB6.php
+++ b/classes/validator/validators/ValidatorB6.php
@@ -57,7 +57,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        if ($this->account{0} !== '0' || preg_match("/^0269[1-9]/", $this->account)) {
+        if ($this->account[0] !== '0' || preg_match("/^0269[1-9]/", $this->account)) {
             $this->validator = $this->mode1;
 
         } else {
diff --git a/classes/validator/validators/ValidatorC1.php b/classes/validator/validators/ValidatorC1.php
index 2e1d7f6..547fc41 100644
--- a/classes/validator/validators/ValidatorC1.php
+++ b/classes/validator/validators/ValidatorC1.php
@@ -56,7 +56,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = $this->account{0} != '5'
+        $this->validator = $this->account[0] != '5'
                          ? $this->mode1
                          : $this->mode2;
     }
diff --git a/classes/validator/validators/ValidatorC3.php b/classes/validator/validators/ValidatorC3.php
index bf312f5..ce07838 100644
--- a/classes/validator/validators/ValidatorC3.php
+++ b/classes/validator/validators/ValidatorC3.php
@@ -57,7 +57,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = $this->account{0} != '9'
+        $this->validator = $this->account[0] != '9'
                          ? $this->mode1
                          : $this->mode2;
     }
diff --git a/classes/validator/validators/ValidatorC4.php b/classes/validator/validators/ValidatorC4.php
index bea79de..216213d 100644
--- a/classes/validator/validators/ValidatorC4.php
+++ b/classes/validator/validators/ValidatorC4.php
@@ -57,7 +57,7 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $this->validator = $this->account{0} != '9'
+        $this->validator = $this->account[0] != '9'
                          ? $this->mode1
                          : $this->mode2;
     }
diff --git a/classes/validator/validators/ValidatorC5.php b/classes/validator/validators/ValidatorC5.php
index 7fba790..ad38f5e 100644
--- a/classes/validator/validators/ValidatorC5.php
+++ b/classes/validator/validators/ValidatorC5.php
@@ -70,25 +70,26 @@ protected function validate()
         $length  = strlen($account);
 
         switch ($length) {
+
             case 6:
             case 9:
-                if ($account{0} < 9) {
+                if ($account[0] < 9) {
                     $this->validator = $this->mode1;
                 }
                 break;
 
             case 8:
-                if ($account{0} >= 3 && $account{0} <= 5) {
+                if ($account[0] >= 3 && $account[0] <= 5) {
                     $this->validator = $this->mode4;
 
                 }
                 break;
 
             case 10:
-                if ($account{0} == 1 || $account{0} >= 4 && $account{0} <= 6 || $account{0} == 9) {
+                if ($account[0] == 1 || $account[0] >= 4 && $account[0] <= 6 || $account[0] == 9) {
                     $this->validator = $this->mode2;
 
-                } elseif ($account{0} == 3) {
+                } elseif ($account[0] == 3) {
                     $this->validator = $this->mode3;
 
                 } else {
diff --git a/classes/validator/validators/ValidatorC6.php b/classes/validator/validators/ValidatorC6.php
index bf6253a..8c5862f 100644
--- a/classes/validator/validators/ValidatorC6.php
+++ b/classes/validator/validators/ValidatorC6.php
@@ -64,8 +64,8 @@ public function __construct(Bank $bank)
 
     protected function validate()
     {
-        $transformation = array_key_exists($this->account{0}, self::$transformation)
-                        ? self::$transformation[$this->account{0}]
+        $transformation = array_key_exists($this->account[0], self::$transformation)
+                        ? self::$transformation[$this->account[0]]
                         : '';
         $this->transformedAccount = $transformation . substr($this->account, 1);
         $this->validator->setNormalizedSize(9 + strlen($transformation));
@@ -76,7 +76,7 @@ protected function validate()
      */
     protected function getResult()
     {
-        return in_array($this->account{0}, array_keys(self::$transformation))
+        return in_array($this->account[0], array_keys(self::$transformation))
              ? $this->validator->isValid($this->transformedAccount)
              : false;
     }
diff --git a/classes/validator/validators/ValidatorD1.php b/classes/validator/validators/ValidatorD1.php
index 9d7d964..6f74647 100644
--- a/classes/validator/validators/ValidatorD1.php
+++ b/classes/validator/validators/ValidatorD1.php
@@ -93,6 +93,6 @@ protected function getResult()
      */
     private function getTransformationIndex()
     {
-        return $this->account{0};
+        return $this->account[0];
     }
 }
diff --git a/classes/validator/validators/ValidatorD4.php b/classes/validator/validators/ValidatorD4.php
index ebc328f..7b0bc54 100644
--- a/classes/validator/validators/ValidatorD4.php
+++ b/classes/validator/validators/ValidatorD4.php
@@ -61,7 +61,7 @@ protected function validate()
      */
     protected function getResult()
     {
-        return $this->account{0} != 0
+        return $this->account[0] != 0
             && $this->validator->isValid($this->transformedAccount);
     }
 }
diff --git a/classes/validator/validators/ValidatorD8.php b/classes/validator/validators/ValidatorD8.php
index 0b2b6e5..293c0a4 100644
--- a/classes/validator/validators/ValidatorD8.php
+++ b/classes/validator/validators/ValidatorD8.php
@@ -53,7 +53,7 @@ protected function validate()
      */
     protected function getResult()
     {
-        if ($this->account{0} != 0) {
+        if ($this->account[0] != 0) {
             return $this->validator->isValid($this->account);
 
         }
diff --git a/classes/validator/validators/ValidatorE2.php b/classes/validator/validators/ValidatorE2.php
index b615be3..8fc16d5 100644
--- a/classes/validator/validators/ValidatorE2.php
+++ b/classes/validator/validators/ValidatorE2.php
@@ -43,7 +43,7 @@ class ValidatorE2 extends Validator
     
     protected function validate()
     {
-        if (in_array($this->account{0}, [6, 7, 8, 9])) {
+        if (in_array($this->account[0], [6, 7, 8, 9])) {
             $this->result = false;
             return;
         }
@@ -51,7 +51,7 @@ protected function validate()
         $validator = new Validator00($this->bank);
         $validator->doNormalization = false;
 
-        $prefixedAccount = self::$prefixes[$this->account{0}] . substr($this->account, 1);
+        $prefixedAccount = self::$prefixes[$this->account[0]] . substr($this->account, 1);
         
         $this->result = $validator->isValid($prefixedAccount);
     }
diff --git a/classes/validator/validators/ValidatorE3.php b/classes/validator/validators/ValidatorE3.php
new file mode 100644
index 0000000..1a2f3bc
--- /dev/null
+++ b/classes/validator/validators/ValidatorE3.php
@@ -0,0 +1,31 @@
+<?php
+namespace malkusch\bav;
+/**
+ * Implements E3
+ *
+ * Copyright (C) 2017  Dennis Ditte <dennis@double-d.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+class ValidatorE3 extends ValidatorChain
+{
+    public function __construct(Bank $bank)
+    {
+        parent::__construct($bank);
+        $this->validators[] = new Validator00($bank);
+        $this->validators[] = new Validator21($bank);
+    }
+
+}
\ No newline at end of file
diff --git a/classes/validator/validators/ValidatorE4.php b/classes/validator/validators/ValidatorE4.php
new file mode 100644
index 0000000..2e1d866
--- /dev/null
+++ b/classes/validator/validators/ValidatorE4.php
@@ -0,0 +1,31 @@
+<?php
+namespace malkusch\bav;
+
+/**
+ * Implements E4
+ *
+ * Copyright (C) 2017 Clemens Weiß <cweiss@webplain.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+class ValidatorE4 extends ValidatorChain
+{
+    public function __construct(Bank $bank)
+    {
+        parent::__construct($bank);
+        $this->validators[] = new Validator02($bank);
+        $this->validators[] = new Validator00($bank);
+    }
+}
\ No newline at end of file
diff --git a/composer.json b/composer.json
index 04eda14..022a7ed 100644
--- a/composer.json
+++ b/composer.json
@@ -1,24 +1,37 @@
 {
-    "name": "malkusch/bav",
+    "name": "rotdrop/bav",
     "type": "library",
     "description": "BAV provides validation for German Bank Accounts (Konto)",
     "keywords": ["bank", "account", "bankaccount", "validation", "check", "konto"],
-    "homepage": "http://bav.malkusch.de/",
+    "homepage": "http://github.com/rotdrop/bav/",
     "license": "WTFPL",
+    "version": "dev-master",
     "authors": [
         {
             "name": "Markus Malkusch",
             "email": "markus@malkusch.de",
             "homepage": "http://markus.malkusch.de",
             "role": "Developer"
+        },
+        {
+            "name": "Markus Zierhut",
+            "email": "markus@zierhut.net",
+            "homepage": "https://markus.zierhut.name",
+            "role": "Developer"
+        },
+        {
+            "name": "Claus-Justus Heine",
+            "email": "himself@claus-justus-heine.de",
+            "homepage": "https://claus-justus-heine.de",
+            "role": "Developer"
         }
     ],
     "autoload": {
         "files": ["autoloader/autoloader.php"]
     },
     "require": {
-        "php": ">=5.4",
-        "malkusch/php-index": "~0.1"
+        "php": ">=7.4",
+        "malkusch/php-index": "dev-master"
     },
     "suggest": {
         "ext-PDO": "Allows storing bank information in a database",
@@ -37,5 +50,13 @@
     "bin": [
         "bin/bav-update.php",
         "bin/bav-install.php"
-    ]
+    ],
+    "repositories": [
+        {
+            "type": "vcs",
+            "url": "https://github.com/bav-php/php-index"
+        }
+    ],
+    "minimum-stability": "dev",
+    "prefer-stable": true
 }