username/password characters

[EXiT]

Hi,

 

  Im looking for a function that will only allow the user to signup

  with the characters: a-z, A-Z, 0-9, - and _

 

  for the username and password fields.

 

  Any code or websites that will show me how this is done, would be

  great.

 

  Cheers

[uniflare]

to validate user input i personally use preg_match.

 

to validate your example you could use this pattern:

 

if(preg_match("/\A[A-Za-z0-9_-]{4,16}",$_POST['username']) != 1){
      echo("Username must be Letters,Numbers,dashes and underscores only, must also be wtween 4 and 16 characters long.");
}else{
      // Username Okay
}

 

http://uk.php.net/manual/en/reference.pcre.pattern.syntax.php for more information on perl-compatible php regular expressions.