How to convert PHP code in 5.4 version to 5.5

Question

I'm learning PHP, anybody helps me to convert this code into PHP 5.5 version, many thanks! I don't know how to replace the function preg_replace with preg_replace_callback. Sorry for my bad English!

$_SERVER['SERVER_NAME'] = preg_replace( array('/^[a-zA-Z]+\:\/\//e'), '', $this->get_Env( array('SERVER_NAME', 'HTTP_HOST') ) );