Do you mean appended to a URL in a browser request?
In PHP, this is the GET method of sending variables from a form page to another PHP script, generally a script that handles the actions needed to do whatever it is you're doing with the information.
As an example, in the URL in your browser now as you read this, you'll see a ?s=somebignumber which is indicating to the server your session id number.
Let's say you had a login page:
<html><head><title>Login</title></head>
<form action="handle.php" method=GET>
Username:<input type=text name=user><br>
Password:<input type=text name=pass><br>
<br><input type=submit value=submit name=submit>
When the user "fred" with the password "me" pushes the submit button, the browser will go to the following URL:
http://site.com/handle.php?user=fred&pass=me
And at that location, you'd code this:
$user=$_GET['user'];
$pass=$_GET['pass'];
if (($user="fred") && ($pass="me")) {
echo "Hi, Fred. Your login was successful, welcome to the site!"
}
Now as you can see, this isn't a real good way to do it*, but it would work, and should give you an idea of PHP's use, although it's much deeper and has much more capability than that. A more secure script would use 'post' as the method instead of 'get'. And there are even better ways to do user authentication. I think I mentioned some sites & books. Read 'em, OK? And do plenty of coding ... you'll probably hate debugging, (most of us do) but learning facts and procedures by experience is the way a lot of folks do stuff these days.
