I've been trying to validate with
FILTER_VALIDATE_REGEXP
I'm trying to allow alphanumeric input but the validation keeps failing when I enter a number
public static function validateUsername($username)
{
return strlen($username) >= self::MIN_USERNAME_LENGTH
&& (strlen($username)) <= self::MAX_USERNAME_LENGTH
&& (filter_var($username , FILTER_VALIDATE_REGEXP,array('options' => array('regexp' => "/^[a-zA-Z0-9]+$/")) === TRUE);
}