How to get a page url segment on wordpress?

Question

I've created a regular wordpress page named "user" which is using a custom template.
This page is supposed to be called like so:
www.site.com/user/<ID>

Is it possible to get the ID segment of the URL programmatically?
The goal is to show the details of the user that belongs to the given ID.

When testing, that part of the URL is always removed.
If I request the URL www.site.com/user/123
the page is redirected to:
www.site.com/user

Thanks in advance.

Answer 1

There are two things that needed here, first add a new rewrite rule and second register the custom query variable.

So in your functions.php

/**
 * Add custom rewrite rule.
 *
 * NOTE: the `user_id` will be registered in the `query_vars` filter below. 
 */
add_action( 'init', function() {
   add_rewrite_rule(
      '^user/([0-9]+)/?',
      'index.php?pagename=user&user_id=$matches[1]',
      'top'
   );
} );


/**
 * Register custom query variables.
 */
add_filter( 'query_vars', function( $vars ) {
   $vars[] = 'user_id';

   return $vars;
} );

And inside your template you can then access the user ID by calling get_query_var( 'user_id' )

Answer 2

yes, you should be able to call the query var by:

get_query_var('user');

if this does not work, then "user" is not the registered query var. You can debug by dumping $wp_query and pin pointing the var / key.

global $wp_query;