如何替换具有未知参数名称的函数？

Question

This is what I want to do:

$var = "foo";  
$unknown = "";  
function do($arg1, $arg2) {  
    $arg2 = "bar";
    magic($arg2);
    }  
do($var, $unknown);  
echo $unknown;

This should return: bar

I know that this would work if I'd define my function like this:

function do($arg1, $unknown) {
    global $unknown;
    $unknown = "bar";
}

As you probably guessed already, the variable name of $unknown is unknown.

I need this because I'm writing a PHP sandbox using apd. I want to replace exec($cmd, $ret) in a PHP script I don't known with my own function.

So if the unknown PHP script looks like this:

$foo = "";
exec('whois google.com', $foo);
echo $foo;

I'll have a problem replacing exec with my own function do() emulating the same functionality.

Answer 1

You want to pass the parameter by reference:

$var = "foo";  
$unknown = "";  
function foo($arg1, &$arg2) {    // NOTE EXTRA "&"
    $arg2 = "bar";
}  
foo($var, $unknown);  
echo $unknown;

See it in action.