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);