checking usernames

ThaSpY

i have a register system im making... where users type in there desired username and submit the form. i want to check to make sure that their username ONLY has a-z, A-Z, 0-9, and underscores. what code would i use to check this? thanks

dankstick

This regexp should help you out...

<?
$name = "good_name";

if(eregi("^[a-z0-9_]+$",$name)){
 //good name
}else{
 //bad name
}
?>

Check out this article for more info on regexp's

http://www.phpbuilder.com/columns/dario19990616.php3

ThaSpY

just what i needed thanks!

ThaSpY

how would i do the opposite? where you are saying IF the name only has those characters, i want IF the name doesnt only have those characters, how would i do that?

laserlight

you can do that with regex too, but isnt one the complement of the other?

In which case a simple NOT logic would be enough.

Also, I suggest using perl compatible regex instead, they are supposedly faster.

ThaSpY

well, see, this is what im trying to do. its a user register system and im using this if statement to check the username for various tihngs:

<? if ($reg_username == "" || $usr_numrows > 0 || !eregi("^[a-z0-9_]+$",$reg_username)) { echo "error"; } else { echo "process"; } ?>

in this example of my code, i've just added a "!" infront of eregi but it hasnt seemed to work. whats the correct way to check what im trying to do here? any suggestions?

goa103

$reg_username == ""

You don't have to compare your string to an empty one, you already check it using the regular expression. Check out the PHPBuilder article for more information.

If you want to inverse your condition if it contains, if it doesn't contain... Simply inverse the if statements :
if () error else process
or
if () process else error
...