How to set up GET error if http headers includes $variables?

In register.inc.php i have this code

   header("Location: ../register.php?u=".$ref."&error=passwordcheck&uid=".$username."&mail=".$email."&name=".$name);
   exit();

and in register this line

   if ($_GET["error"] == "&error=passwordcheck&uid=&mail=&name=") { ?>
                     <div class="alert alert-danger alert-dismissible fade show" role="alert">
            Passwords dont match!

Usually it works but on this page the alert is not showing up to the user if the passwords dont match. What am i doing wrong?

this is the header in case of error in frontend

mydomainname.com/register.php?u=0&error=passwordcheck&uid=test1&mail=test1@gmail.com&name=test

edit: I feel ashamed asking such an easy question when i have solved much harder issues.

>Solution :

You have not understood HTTP query string parsing.

Here’s how it works: the query strings are separated using &, so:

?u=0&error=passwordcheck&uid=test1&mail=test1@gmail.com&name=test

is split into:

1. u = 0
2. error = passwordcheck
3. uid = test1
4. mail = test1
5. name = test

So, use:

   if ($_GET["error"] == "passwordcheck") { ?>
                     <div class="alert alert-danger alert-dismissible fade show" role="alert">
            Passwords dont match!