$_GET check if exists and not a letter

[Tijmen]

Hi,

I'm trying to check if the user_id is set, and if it's a number instead of a letter. If any of these 2 fail it should redirect the page back to the index.

This works for the first part, if the user_id is not in the url you are going back to the index. But when i enter a letter instead of a number it only comes up with an error. I try'd the is_numeric check seperately and this works fine, but i can't get it to work together.

Any suggestions how to fix it, or a better way to make sure the user_id is a number and does exist in the url.

 if(!isset($_GET['user_id']) && (!is_numeric($_GET['user_id']))) { 
   header ("Location: http://" . $_SERVER['HTTP_HOST'] . dirname($_SERVER['PHP_SELF']) . "/index.php");
 }

[lilleman]

You have to use or instead of and, since you want the IF-statement to be true when one condition fail:

if(!isset($_GET['user_id']) or !is_numeric($_GET['user_id'])) { 

[Tijmen]

Thanks, works beter now.

[shiflett]

You might also want to use ctype_digit() instead of is_numeric(). They're similar, but ctype_digit() returns TRUE when all characters are a digit. This is different than is_numeric(), which returns TRUE for any valid representation of a number.