Nothing different; these are already both strings, so the results would be the same. Identical is used for conflicting datatypes like checking 0 === false which is false, while 0 == false is true.
As of PHP 5.5, the MySQL library has been officially deprecated. It is recommended to move to either MySQLi or PDO libraries for your mysql connectivity. See here for help choosing which interface you prefer: http://php.net/manual/en/mysqlinfo.api.choosing.php