PHP中的指针问题[重复]

Question

Possible Duplicate:
Strange behavior Of foreach
Strange behaviour after loop by reference - Is this a PHP bug?

Can anybody explain me why this code:

<pre>
<?php

$a = array('page', 'email', 'comment');
$b = array('page' => 'realpage', 'email' => 'reaLmail', 'comment' => 'c');
$c = array();

foreach ($a as &$item) {
        if (isset($b[$item])) {
               $item =  $b[$item];
        }
}


foreach ($a as $item) {
        $c[] = $item;
}

print_r($c);

Outputs

 Array
(
    [0] => realpage
    [1] => reaLmail
    [2] => reaLmail
)

??? Why BEFORE second loop a is (by var_dump)

array(3) {
  [0]=>
  string(8) "realpage"
  [1]=>
  string(8) "reaLmail"
  [2]=>
  &string(1) "c"
}

But in first iteration, a is

 array(3) {
  [0]=>
  string(8) "realpage"
  [1]=>
  string(8) "reaLmail"
  [2]=>
  &string(8) "realpage"
}

and on second and third [1] and [2] indexes are the same "reaLmail", and [2] is pointer? Thank you!

Answer 1

if you use foreach (... as &..), then unset is required as describe in the php manual:

foreach ($a as &$item) {
        if (isset($b[$item])) {
               $item =  $b[$item];
        }
}
unset($item);