Fixes after code review

Author: karyna-t

library/Zend/Db/Adapter/Pdo/Abstract.php

@@ -293,7 +293,7 @@ protected function _quote($value)
             return $value;
         }
         $this->_connect();
-        return $this->_connection->quote($value ?? '');
+        return ($value !== null) ? $this->_connection->quote($value) : '""';
     }
 
     /**

library/Zend/Db/Select.php

@@ -817,10 +817,9 @@ protected function _join($type, $name, $cond, $cols, $schema = null)
             $tableName = $name;
             $correlationName = $this->_uniqueCorrelation($tableName);
         }
-        $tableName = $tableName ?? '';
 
         // Schema from table name overrides schema argument
-        if (!is_object($tableName) && false !== strpos($tableName, '.')) {
+        if ($tableName && !is_object($tableName) && (strpos($tableName, '.') !== false)) {
             list($schema, $tableName) = explode('.', $tableName);
         }
 

library/Zend/Http/Response.php

@@ -261,7 +261,7 @@ public function getBody()
         $transferEncoding = $this->getHeader('transfer-encoding');
 
         // Decode the body if it was transfer-encoded
-        switch ($transferEncoding ? strtolower($transferEncoding) : '') {
+        switch (($transferEncoding !== null) ? strtolower($transferEncoding) : '') {
 
             // Handle chunked body
             case 'chunked':
@@ -278,7 +278,7 @@ public function getBody()
         $contentEncoding = $this->getHeader('content-encoding');
 
         // Decode any content-encoding (gzip or deflate) if needed
-        switch ($contentEncoding ? strtolower($contentEncoding) : '') {
+        switch (($contentEncoding !== null) ? strtolower($contentEncoding) : '') {
 
             // Handle gzip encoding
             case 'gzip':

library/Zend/Locale/Data.php

@@ -982,7 +982,7 @@ public static function getContent($locale, $path, $value = false)
         if (is_array($value)) {
             $val = implode('_' , $value);
         }
-        $val = $val ? urlencode($val) : '';
+        $val = ($val !== null) ? urlencode($val) : '';
         $id  = self::_filterCacheId('Zend_LocaleC_' . $locale . '_' . $path . '_' . $val);
         if (!self::$_cacheDisabled && ($result = self::$_cache->load($id))) {
             return unserialize($result);

library/Zend/Oauth/Http/Utility.php

@@ -210,6 +210,7 @@ public function generateTimestamp()
      */
     public static function urlEncode($value)
     {
-        return $value ? str_replace('%7E', '~', rawurlencode($value)) : '';
+        return ($value !== null) ?
+            str_replace('%7E', '~', rawurlencode($value)) : '';
     }
 }

library/Zend/Validate/File/Extension.php

@@ -121,9 +121,7 @@ public function setCase($case)
      */
     public function getExtension()
     {
-        $extension = explode(',', $this->_extension);
-
-        return $extension;
+        return ($this->_extension !== null) ? explode(',', $this->_extension) : [''];
     }
 
     /**