[PHP] SQ: what does the & sign do

[Wilbert Enserink]

Hi all,


maybe this is a stupid Q, but lately I'm diving into OOP. Below you can see a piece of 
example code from the manual. 
my Q: what does the & sign do in functioncb_modify( &$item,$key) ??

I noticed this sign is used more, so it should be handy, but hwat does it do?

thx Wilbert

-----------------------------


class mod {
    var $thearray;
    function mod( $a ) {
      $this->thearray = $a;
    }
    function cb_modify( &$item, $key ) {
      $item = "pref_".$item;
    }
    function modify() {
      array_walk( $this->thearray, array( $this, 'cb_modify' ) );
    }
  }
  $m = new mod(array("one","two","three"));
  $m->modify();
  print_r($m);

which prints out:

  mod Object
  (
      [thearray] => Array
          (
              [0] => pref_one
              [1] => pref_two
              [2] => pref_three
          )
  )




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