Routing algorithm for Wordpress - wordpress

Question

I don't know the exact meaning of the question but someone asked me this question in interview. I just want to know that there's something like that, we use any route algorithm in Wordpress?

Answer 1

This could be a trick question because routing would mean mapping an HTTP request to trigger specific function or method that would handle the request which is not something that WordPress does (there is a section about WordPress at the bottom). In simple word, you read the HTTP request information to decide what function is going to be triggered.
Bit more details in simple words
if you are building a PHP project from scratch and want to display specific content or trigger a method/function there are usually two option (without routing)
Using POST , GET or REQUEST variables and complex conditional statements to achieve what you want, so a result URL could be something like this
http://example.com/index.php?view=pubications&per_page=5
Setting a PHP file for each type of content
http://example.com/publications.php?per_page=5
However, if you created a Router (Routing algorithm as you named it or routing system) then pushed all requests to index.php and have the latter include let's say something like this:
// Include the Router class
require('classes/router.php');
// Include functions responsible for display our content
require('view/display.php');
I'll not go into how to build a router, just giving examples assuming that you already have one just to give you an idea how routing works.
So assuming you have a router and function to display a contact form for example, you'd also include something like this:
Router::add('/contact-us', get_contact_form(),'get');
Router::add('/contact-us', handle_contact_form(),'post');
Then initialize the Router
Router::initialize('/');
Again assuming you have a complete Router, the above function would tell the index.php file to handle HTTP requests on this URL differently:
http://example.com/contact-us
If it's the default request type GET, trigger this function get_contact_form(), but if the request type is POST trigger this one handle_contact_form() which will act and display content differently depending on your needs.
That's great because it would be instead of something like
http://example.com/index.php?page=contact-us
index.php content would handle the request differently since there is no router.
// Include functions responsible for display our content
require('view/display.php');
if( isset($_GET['page']) && $_GET['page'] == 'contact-us'){
echo get_contact_form();
}
if( isset($_GET['page']) && $_GET['page'] == 'contact-us' && isset($_POST['contact_submit']) ){
echo handle_contact_form();
}
Imagine how long and ugly this would look like if you have a lot of pages and a complex site.
So back to WordPress
If you have a new installation you'd notice that the URLs looks something like this:
http://example.com/?p=62
http://example.com/?cat=1
http://example.com/?author=3
So it would just take URL parameters then build a WP_Query based on that, if is p then look for posts in database by ID, if cat then look for categories by ID and so on... (that's the simple explanation, there is a lot going on of course in the back-end, but just to give an idea).
You might notice after changing permalink structure that the above examples would now look something like this:
http://example.com/post-slug
http://example.com/author/name
http://example.com/category/uncategorized
This might look like routing, but it isn't, let's go in a bit more details about how this works.
When requesting a (pretty-link) URL on WordPress, first thing that happens is that the .htaccess looks for a folder/file with same name on the server, if it exists it will served, if not, it would send that request to the index.php file which does one thing:
/** Loads the WordPress Environment and Template */
require( dirname( __FILE__ ) . '/wp-blog-header.php' );
loading the wp-blog-header.php file, which will make a small check to make sure the code only run once then the following:
// Load the WordPress library.
require_once( dirname(__FILE__) . '/wp-load.php' );
// Set up the WordPress query.
wp();
// Load the theme template.
require_once( ABSPATH . WPINC . '/template-loader.php' );
Let's not go deeper into these files, what's concerns us the most is what 'wp-load.php' and 'template-loader.php' does
wp-load.php
This one among other things, looks for wp-config, make sure everything is set correctly, then connect to the database, of course after a lot of initialization, setting up constants loading a lot files that handles different parts of WordPress structure. Part of this process is that WordPress tries to match the request URL with a large set of rule called rewrite rules which are set of regular expressions, when a match is found WordPress will translate that URL into a database query using [WP_Query][1] class which is located at wp-includes/class-wp-query.php and this class will save the query results among other things (query type...etc)
template-loader.php
This one handles the display part, it uses some WordPress function that make use of WP_Query (eg:is_home()) to find out what type of content is to be displayed, then loads the the correct template based on that, and finally the template will use WP_Query to show the result.