is there an alphanumeric php function?

[sde]

i thought there was a php function for matching alphanumeric strings, but i can't find it.

i thought this would work, but it does not seem to. i can use preg_match(), but i didn't think i'd have to.

[sde]

my preg match doesn't work .. can someone help me?

PHP Code:

<?
if(!preg_match("([a-zA-Z0-9]*)","$nick"))
{
  $this->error.="<li>Username must be alphanumeric.";
}
?>

[sde]

i took the * out and it works fine.