mattonomics

I’d like to introduce a few concepts in this tutorial regarding WordPress and query strings. First of all, I understand that many of you will likely never deal with query strings and if you do (hopefully) you never even notice them. By “not noticing” query strings, I mean that whatever service is hopefully passing information to your site that doesn’t cause WordPress to 404. That, of course, means that the developers of such services need to be aware of the WordPress reserved terms.

What is a query string?

Have you ever been to a website and seen a bunch of nonsense after the url? Here is an example (non-functional) of what I mean:

// url without query string

http://thesistutor.com

// url with querystring

http://thesistutor.com?this=that&foo=bar&love=coffe&hate=24season8

That is pretty straightforward, I believe. Just think of everything after the ? as an array like this:

$query_array = array( 'this' => 'that', 'foo' => 'bar', 'love' => 'coffee', 'hate' => '24season8' );

In PHP there is a special predefined variable called $_GET that produces an array similar to the one above. Basically, this allows developers to literally get information passed to a site from a URL. This is extremely convenient and simple to use. For example, to get the value of love we would simply use $_GET["love"]. A practical example would be like this:

<?php

// outputs 'I see that you love coffee.'
echo 'I see that you love ' . $_GET["love"] . '.';

// or if you're awesome
printf( 'I see that you love %s.', $_GET["love"] );

?>

WordPress Reserved Terms

Unfortunately, there are a ton of variables that you can’t pass to WordPress or else you will get a 404 page. Some are very common terms, sadly. For instance, you cannot use name, calendar, link, more, year, type and many other terms. So what do you do if one of those terms is passed to your site? You certainly don’t want a 404 error.

I have seen a TON of tutorials that purport to have solved this problem with Apache rewrite rules. I think that technique is ridiculous and very unsafe. So, how can we rectify this without using outrageous Apache rewrite rules?

The solution is quite simple, actually.

The Code

First of all, it would be very atypical to desire every single page of a site to accept a reserved term. Most likely, it is just one or two pages. And even more likely, it is a single term and not plethora of them.

So here is the basic flow of how this will work. First we test to make sure we are on the desired page and that the reserved term is present in the query string. Then we will take the reserved term and simply rename it! For the sake of this example, we will assume that you are receiving the reserved term on a page whose id is 72. We’ll also assume that the reserved term you are going after is “link.”

<?php
add_action( 'wp' , 'reserved_term_intercept' );

function reserved_term_intercept(){
  global $wp_query;
  if( $wp_query->queried_object_id == 72 && isset( $_GET["link"] ) ){

    wp_redirect( get_permalink( 72 ) . "?newlink=" . $_GET["link"] . "&nonce=" . wp_create_nonce( 'nonce-name' ) );
    exit;
    }
  }
?>

Basically all we are doing is redirecting the page to itself and serving a modified query string. You also likely noticed that I added a nonce for some added security. Once the page has redirected, we need something to handle the modified query string. We could do something like this:

<?php

add_action( 'wp_head' , 'reserved_term_handling' );

function reserved_term_handling(){

  if( wp_verify_nonce( $_GET["nonce"], 'nonce-name' ) == TRUE && isset( $_GET["newlink" ) ){
    printf( '<script type="text/javascript" src="%s"></script>', urldecode( $_GET["newlink"] ) );
  }
}
?>

That’s all there is to it! No Apache rewrites. No messing with classes you don’t understand. Quick and simple, just the way developers like it

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