Prevent special character in username

[marSoul]

Hi
I want prevent users to enter a username with special characters like space when they are registering a new one.
How can i do it ?
Is it regular expression or something else ?
thnx

[AdRock]

Yes you need to use a regular expression. This one only allows letters and numbers and uses the variable $username which would be $_POST['username']

PHP: Select all

if(!ereg("^[A-Za-z0-9]{4,30}$",$username)) {
    //do error code here
} 

[marSoul]

Thanx

[AdRock]

also you can set the amount of characters you are allowing between the curly braces.

In my example you are allowing between 4 and 30 charaters