Question

I know the title isn’t very clear. I’m new to PHP, so there might be name for this kind of thing, I’ll try to explain as best as I can. Sometimes in a URL, when using PHP, there will be a question mark, followed by data. I’m sorry, I know this is very noobish, but I’m not sure what it’s called to look for a tutorial or anything. Here is what I mean:

http://www.website.com/error_messages.php?error_id=0

How do you configure it to display different text depending on what the number is (in this example it’s a number)

Could somebody please tell me what this is called and how I could do this? I’ve been working with PHP for a couple days and I’m lost. Thank you so very much for understanding that I am very new at this.

Answer 1

That “data” is the URL querystring, and it encodes the GET variables of that HTTP request.

Here’s more info on query strings: http://en.wikipedia.org/wiki/Query_string

In PHP you access these with the $_GET “super-global” variable:

// http://www.website.com/error%5Fmessages.php?error%5Fid=0
// %5F is a urlencoded '_' character, which your webserver will most likely
// decode before it gets to PHP.
// So ?error%5Fid=0 reaches PHP as the 'error_id' GET variable
$error_id = $_GET['error_id'];
echo $error_id; // this will be 0

The querystring can encode multiple GET variables by separating them with the & character. For example:

?error_id=0&error_message=Something%20bad%20happened

• error_id => "0"
• error_message => "Something bad happened"

In that example you can also see that spaces are encoded as %20.

Here’s more info on “percent encoding”: http://en.wikipedia.org/wiki/Percent-encoding