Entry

Is it faster to pass a global variable to a function as an argument?

Mar 3rd, 2000 10:59
Hamish Allan, Nathan Wallace, http://www.php.net/manual/functions.arguments.php3

There are three methods to access a global variable inside a function:

1. Having a (global) variable, setting it to "global" inside a function.

    $language='EN';
    function foo($param) {
        global $language
        ...
    }

2. Having a (global) variable, passing it with the function call to the
function.

    $language='EN';
    function poo($param, $language) {
        ...
    }

3. Having a (global) variable, passing it by reference with the 
function call to the function.

    $language='EN';
    function noo($param, &$language) {
        ...
    }

The first and third methods are functionally equivalent, but the second 
makes a copy (pass by value), which has two effects:

a. Space and time overheads are incurred on the copy.
b. Any changes to $language are local, so if we put the line:

     $language=$param;

   into each of our functions foo(), poo() and noo(), the behaviour is 
as follows:

     $language='EN';
     foo('FR');
     echo $language; // outputs FR
     poo('DE', $language);
     echo $language; // outputs FR
     noo('ES', $language);
     echo $language; // outputs ES