wordpress-nginx-flush-cache.php

<?php

/**
 * Plugin Name: NGINX FastCGI cache purge
 * Version: 0.1
 * Description: Flush NGINX FastCGI cache purge
 * Author: The Shipyard Crew
 * Author URI: https://theshipyard.se/
 * Plugin URI: https://theshipyard.se/
 * Text Domain: nginx-fastcgi-cache-purge
 * @package NGINX FastCGI cache purge
 */

if ( ! defined( 'NGINX_CACHE_PATH' ) ) {
    define( 'NGINX_CACHE_PATH', '/var/run/nginx-cache' );
}

final class NGINX_FastCGI_cache_purge {

    public static $instance = null;

    private function __construct() {
        add_action( 'edit_post', [ $this, 'purge_cache' ] );
    }


    /**
     * Creates or returns an instance of this class.
     *
     * @return A single instance of this class.
     */
    public static function init() {
        if ( self::$instance === null ) {
            self::$instance = new self;
        }

        return self::$instance;
    }


    /**
     * Purge a page from the NGINX FastCGI cache.
     *
     * @param int $post_id WP_Post ID.
     */
    public function purge_cache( $post_id ) {
        if ( 'publish' !== get_post_status( $post_id ) ) {
            return;
        }

        $public_post_types = get_post_types([ 'public' => true ]);
        $post_type = get_post_type( $post_id );
        if ( ! in_array( $post_type, $public_post_types ) ) {
            return;
        }

        $url = get_permalink( $post_id );
        if ( ! $url ) {
            return;
        }

        $path = $this->get_cache_path( $url );
        if ( $path ) {
            $this->flush_cache( $path );
        }
    }


    /**
     * Get the path to the cached file from the URL.
     *
     * @param string $url URL to parse.
     *
     * @return string path to the cached page.
     */
    protected function get_cache_path( $url ) {
        if ( ! $url ) {
            return false;
        }

        $url = parse_url( $url );
        $hash = md5( $url['scheme'] . 'GET' . $url['host'] . $url['path'] );
        $path = trailingslashit( NGINX_CACHE_PATH );

        return $path . substr( $hash, -1 ) . '/' . substr( $hash, -3, 2 ) . '/' . $hash;
    }


    /**
     * Flush the cache from the path to the cached file.
     * 
     * @param string $path Path to the cached file to flush.
     * 
     * @return bool True on success or false.
     */
    protected function flush_cache( $path ) {
        if ( file_exists( $path ) ) {
            return unlink( $path );
        }

        return false;
    }

}

NGINX_FastCGI_cache_purge::init();