Help validating username

[adammc]

Hi guys,

I am trying to validate a username input on my form using regular expression.

The username can only have letters, numbers, underscores a single period. I dont want them to be able to use spaces and caps (possibly converting all chars to lowercase?)


Can anyone help?

[adammc]

I got it sorted using:

// check for a valid username
$pattern = "/^([a-zA-Z0-9._])+$/"; 
if(!preg_match($pattern,$_POST['username'])) { 
$errors[] = 'Please enter a valid username.';
} else { 
// if it passes validation, convert to lowercase 
$username = strtolower($username);

}