I won’t incriminate this project’s coders, but they do sell their work that is based on vBulletin. One of their free projects contains a function that has three arguments passed to it. The first argument is immediately overwritten by a global. Here is a stripped down example:

<?php
$hello = 'hello';
$world = 'world';

function test(&$hello) {
    global $hello;
    echo "$hello\n";
}

test($world);
echo "$hello $world\n";

?>

And the output of my function:

$ php test.php
hello
hello world

$world is passed by reference as $hello. It is promptly ignored in favor of the global $hello variable, without even overwriting $world. They should remove the required parameter $hello.