If you need show some errors in your php code - use this php notation:

// enable showing errors in PHP
ini_set('error_reporting', E_ALL & ~E_NOTICE & ~E_WARNING & ~E_STRICT);
ini_set('display_errors','On');

<?php  
if ( ! function_exists ( 'yours_func' )) {
    function yours_func() {
     ...
    }
 }
?>