PHP runkit_function_rename don't work?

Question

This code don't work. Why not?

<?php
function test()
{
    echo 'test';
}
runkit_function_rename('test', 'test2');
test2();
?>

What I really want is this. I'm using a system that have a function. When I'm on localhost I want that function to do something different. I want to override the function with own stuff.

All alternatives are welcome as well.

Answer 1

Do you have the PECL extension installed?

http://www.php.net/manual/en/runkit.installation.php

This » PECL extension is not bundled with PHP.