What does "&" mean here in PHP?

Question

call_user_func(array(&$this, 'method_name'), $args);

I know it mean pass-by-reference when defining functions,but is it when calling a function?

Answer 1

Its a pass-by-reference.

Answer 2

It's pass by reference. Instead of creating a copy to go into the function, it will send the actual variable..

$string = 'test';

hello($string);

function hello(&$s) {
    $s .= ' and some more test';
}

// IIRC, the output will be 'test and some more test'

Update

call_user_func(array(&$this, 'method_name'), $args);

I think this code will call a method name within that class, and send $args as parameters. The pass by reference I assume is that it won't attempt to copy the $this, (I'm not sure if it even can). $this would be the reference to the class.

Answer 3

From the Passing By Reference docs page:

You can pass a variable by reference to a function so the function can modify the variable. The syntax is as follows:

<?php
function foo(&$var)
{
    $var++;
}

$a=5;
foo($a);
// $a is 6 here
?>

...In recent versions of PHP you will get a warning saying that "call-time pass-by-reference" is deprecated when you use & in foo(&$a);