Problem with preg_match

[callumd]

Hello all,

I am trying to ensure that a given username consists of alpha-numeric characters only. Here's the code:

<?php
$username = "madmax's";
if (preg_match('/[1-9|a-z|A-Z]{6,14}/', $username)) {
    echo 'Preg.. MATCH! $username is: ' . $username . '<br />';
} else {
    echo 'No preg_match. Username may consist of alpha-numeric characters only';
}
?>

And here's the output to the browser:
---
Preg.. MATCH! $username is: madmax's
---

What's wrong with my code? The apostrophe in madmax's should have meant the pregmatch failed..

[NogDog]

if(preg_match('/^[a-z0-9]{6,14}$/i', $username)) {