passing parameters to function: PHP4 and PHP5

Variables

In PHP4 and PHP5, variables by default are passed by value (copy) to functions. It means that outside the function the variables don't change

$v = 1;
function increment($v) { $v++; }
increment($v);
print $v; // 1 !!

If you want to pass by reference, use the operator &

$v = 1;
function increment(&$v) { $v++; }
increment($v);
print $v; // 2 !!

Objects

by default:

• PHP4: object passed by value
  inside the function, the passed object are cloned !
• PHP5: object passed by reference
  equivalent explanation: the reference of the object is passed by value

class A{ public $val;}
function incrementA($a){$a->val++; }
$a = new A(); $a->val = 1;
print $a->val; // PHP4 and PHP print "1"
incrementA($a);
print $a->val; // PHP4 prints "1", PHP5 prints "2"