Only allowing certain characters

[tibberous]

I am trying to only allow letters and numbers in the usernames for my site. Does anyone know what function checks to make sure a username like that is valid?

[pocobueno1388]

EDIT: Oops, code edited, works now.

 

With REGEX

 

<?php

$username = "someUsername";

if (!eregi("[^a-zA-Z0-9]", $username)){
   echo "VALID";
} else {
   echo "INVALID";
}

?>

 

 

[Daniel0]

if(ctype_alnum($username))
{
echo "valid";
}
else {
echo "invalid";
}

 

Faster