libraries/common.lib.php might have not been loaded by the time PMA_isSerializable() is called.

libraries/Error.class.php

@@ -169,7 +169,11 @@ class PMA_Error extends PMA_Message
      */
     public function getHash()
     {
-        $backtrace = PMA_isSerializable($this->getBacktrace()) ? serialize($this->getBacktrace()) : '';
+        try {
+            $backtrace = serialize($this->getBacktrace());
+        } catch(Exception $e){
+            $backtrace = '';
+        }
         if (null === $this->_hash) {
             $this->_hash = md5(
                 $this->getNumber() .

libraries/common.lib.php

@@ -3022,21 +3022,4 @@ function PMA_buildActionTitles() {
     $titles['Edit']       = PMA_getIcon('b_edit.png', __('Edit'), true);
     return $titles;
 }
-
-/**
- * Determines whether a variable is serializable.
- *
- * @param object $var object which needs to be checked for serializability
- *
- * @return whether the object is serializable.
- */
-function PMA_isSerializable($var)
-{
-    try {
-        serialize($var);
-        return true;
-    } catch(Exception $e) {
-        return false;
-    }
-}
 ?>