validating username and password

[frijole]

I am trying to validate usernames and passwords for a registration. I only want to allow letters and numbers. here is what I have, does this make sense?

 

foreach($_POST as $field => $value)
       {
       if (!empty($value)
       {
	       if (eregi("name", $field) and !eregi ("login", $field))
	       {
		       if (eregi("^[A-Za-z' -]{1,50}$",$value))
		       {
			       $errors[] = "$value is not a valid name.";
		       }
	       }

       }
       }

[marcus]

if(!ctype_alnum($value)){
     $errors[] = "Invalid name";
}

[frijole]

thanks, just what I was looking for. SOLVED