Wordpress plugin to create virtual page using rewrite rules - php

Question

I'm creating a plugin that will need virtual pages to output content on the front end.
Here is my code:
add_filter( 'generate_rewrite_rules', function ( $wp_rewrite ) {
$wp_rewrite->rules = array_merge(
['my-custom-url/?$' => 'index.php?custom=1'],
$wp_rewrite->rules
);
} );
add_filter( 'query_vars', function( $query_vars ) {
$query_vars[] = 'custom';
return $query_vars;
} );
add_action( 'template_redirect', function() {
$custom = intval( get_query_var( 'custom' ) );
if ( $custom ) {
include plugin_dir_path( __FILE__ ) . 'templates/states.php';
exit();
}
} );
In the plugin I have templates/states.php and in that file I have:
<?php
$state = get_query_var( 'custom' );
echo $state;
?>
When I visit localhost/my-custom-url/somevariable I get a page not found from Wordpress. I've tried flushing my permalinks.

Answer 1

As I said in the comments
I have never used generate_rewrite_rule
The documentation on it is pretty weak too. But this key looks just like I would expect a Regular expresion to be. And, that makes sense as that is how real Mod Rewrite and Htaccess work.
add_filter( 'generate_rewrite_rules', function ( $wp_rewrite ) {
$wp_rewrite->rules = array_merge(
['my-custom-url/?$' => 'index.php?custom=1'],
$wp_rewrite->rules
);
} );
So this $ here matches the end of the string, this means your URL must end with my-custom-url with an optional / because of the ?.
When I visit localhost/my-custom-url/somevariable I get a page not found
That's not surprising as your URL does not end in a way that will match that pattern.
Test it yourself!
So you can just remove the $ you may or may not want to keep the / optional.
add_filter( 'generate_rewrite_rules', function ( $wp_rewrite ) {
$wp_rewrite->rules = array_merge(
['my-custom-url/?' => 'index.php?custom=1'],
$wp_rewrite->rules
);
} );
One note is this will make that match anywhere in the URL
Test this one
Hope it works.