Description:
------------
I can't understand why I'm getting wrong output
http://codepad.org/nWTjjjV6

Test script:
---------------
<?php
$spell = array("double", "toil", "trouble", "cauldron", "bubble");
foreach ($spell as &$word) {
    $word = ucfirst($word);
    echo $word . "\n";
}
echo "---\n";
foreach ($spell as $word) {
    echo $word . "\n";
}

Expected result:
----------------
Double
Toil
Trouble
Cauldron
Bubble
---
Double
Toil
Trouble
Cauldron
Bubble

Actual result:
--------------
Double
Toil
Trouble
Cauldron
Bubble
---
Double
Toil
Trouble
Cauldron
Cauldron