Php exit function question

Question

I have noticed a behavior in PHP that makes sense, but I am unsure how to get around it.

I have a long script, something like this

<?php 
 if ( file_exists("custom_version_of_this_file.php") ) {
  require_once "custom_version_of_this_file.php";
  exit;
 }
 // a bunch of code etc
 function x () {
  // does something
 }
?>

Interestingly, the function x() will get registered with the script BEFORE the require_once() and exit are called, and therefore, firing the exit; statement does not prevent functions in the page from registering. Therefore, if I have a function x() in the require_once() file, the script will crash.

Because of the scenario I am attempting (which is, use the custom file if it exists instead of the original file, which will likely be nearly identical but slightly different), I would like to have the functions in the original (calling) file NOT get registered so that they may exist in the custom file.

Anyone know how to accomplish this?

Thanks

Answer 1

You could use the function_exists function. http://us.php.net/manual/en/function.function-exists.php

if (!function_exists("x")) {
    function x()
    {
        //function contents
    }
}