Call By Reference

• Use & to pass by reference.

<?php
   function square1($number) {
      return $number * $number;
   }

   $val = square1($val);

   function square2(&$number) {
      $number = $number * $number;
   }

   square2($val);
?>

• Or to return by reference:

<?php
   function &square1($number) {
      return $number * $number;
   }

   $val =& square1($val);
?>