Question

I know this question seems hacky and weird, but is there a way to remove a function at runtime in PHP?

I have a recursive function declared in a "if" block and want that function to be "valid" only in that "if" block. I don’t want this function to be callled outside this block.

I found out runkit_function_remove but runkit isn’t enabled on my Web host. Is there another way to do that?

BTW I only support PHP 5.1.0.

Edit: I knew my question was hacky but here is the exact thing I want to do:

if (function_exists('get_magic_quotes_gpc') && @get_magic_quotes_gpc())
{
    function stripslashes_deep($value)
    {
        return is_array($value) ? array_map('stripslashes_deep', $value) : stripslashes($value);
    }

    $_POST = array_map('stripslashes_deep', $_POST);
    $_GET = array_map('stripslashes_deep', $_GET);
    $_COOKIE = array_map('stripslashes_deep', $_COOKIE);
    $_REQUEST = array_map('stripslashes_deep', $_REQUEST);

    //runkit_function_remove('stripslashes_deep');
}

Since "stripslashes_deep" will only live when Magic Quotes are ON, I wanted to get rid of it when I’m done with it. I don’t want people to rely on a function that isn’t always there. I hope it’s clearer now. Non-hacky solution suggestions are welcome too!

Answer 1

From the PHP Manual on user-defined Functions:

All functions and classes in PHP have the global scope – they can be called outside a function even if they were defined inside and vice versa. […] PHP does not support function overloading, nor is it possible to undefine or redefine previously-declared functions.

The exception is through runkit. However, you could define your function as an anonymous function and unset it after you ran it, e.g.

if (function_exists('get_magic_quotes_gpc') && @get_magic_quotes_gpc()) {
    $fn = create_function('&$v, $k', '$v = stripslashes($v);'); 
    array_walk_recursive(array(&$_GET, &$_POST, &$_COOKIE, &$_REQUEST), $fn);
    unset($fn);
}

Some commentors correctly pointed out (but not an issue any longer in PHP nowadays), you cannot call an anonymous function inside itself. By using array_walk_recursive you can get around this limitation. Personally, I would just create a regular function and not bother about deleting it. It won’t hurt anyone. Just give it a proper name, like stripslashes_gpc_callback.

Note: edited and condensed after comments