Question

I know that in PHP when you want the function parameters to reference target variables we use the ampersand & sign. But I can not figure out if it is still valid and reliable in the following scenario (where variables are gathered from a request).

$v1 = $_POST['v1'];

function filled(&$var) {
    return isset($var) && !empty($var);
}

if (!filled($v1)) // etc.

or even in this scenario:

$v1 = $_POST['v1'];
$v2 = $_POST['v2'];

function filled() {
    $args = &func_get_args(); // does this even take the references and not the values?
    foreach ($args as &$arg) {
        if (empty($arg) || !isset($arg)) return false;
    }
    return true;
}

if (!filled($v1, $v2)) // etc.

Thanks in advance for clarification.

Answer 1

It is still valid since references don’t care if the variables are user defined or come from PHP superglobals, but there are a couple of issues with your first example.

First, when you do $v1 = $_POST['v1']; $v1 is now independent of the $_POST['v1'] variable. Any changes to $v1 are not reflected in $_POST['v1'] because you made a copy.

You could do: $v1 = &$_POST['v1']; to create a reference to it.

Second, your call to isset in the function will always return true. isset is a special language construct, and not a function. If $_POST['v1'] is unset, $v1 will still be set (but will be null) after the assignment of $_POST['v1'] to $v1.

Also, as far as I know, func_get_args() doesn’t support references, all the values it returns are copies of the original.

Does that clear up some of your questions? If not, feel free to ask on anything you want clarified.