PHP5 foreach loop using reference variable

// In PHP5 foreach loop using reference variable
// Example
$arr = array(2,3,4,5);
print_r($arr); // Array ( [0] => 2 [1] => 3 [2] => 4 [3] => 5 )
foreach ($arr as &$value) {
if($value == 4) { $value = 77; }
}
print_r($arr); // Array ( [0] => 2 [1] => 3 [2] => 77 [3] => 5 )