gistfile1.php

<?php

require __DIR__ . "/path/to/Patchwork.php";

use Patchwork\Preprocessor as pp;

pp\attach(array(function(pp\Source $s)
{
	$needle = "var_dump"; # The function to replace
	$replacement = "customDump"; # The replacement
	foreach ($s->findAll(T_STRING) as $offset) {
		if ($s->tokens[$offset][pp\Source::STRING_OFFSET] === $needle) {
			$s->splice($replacement, $offset, 1);
		}
	}
}));

require __DIR__ . "/your_code.php";