http://tangrufus.com/wordpress-plugin-boilerplate-tutorial-hooks-and-http-api

class-sunny-demo-admin.php

<?php
// sunny-demo/admin/class-sunny-demo-admin.php

class Sunny_Demo_Admin {

	// Some code is skipped!!!!!!!

	/**
	 * Initialize the plugin by loading admin scripts & styles and adding a
	 * settings page and menu.
	 *
	 * @since     1.0.0
	 */
	private function __construct() {

		// Few lines skipped!!!!!!!

		// Load includes
		add_action( 'admin_init', array( $this, 'load_includes' ) );

		// Add the option settings
		add_action( 'admin_init', array( 'Sunny_Demo_Option', 'get_instance' ) );

		// Initialize Sunny_Demo_Post_Purger during post saving
		add_action( 'save_post', array( 'Sunny_Demo_Post_Purger', 'get_instance' ), 5 );

	}

	// Lots of lines skipped here!!!!!!!

	/**
	 * This function loads files in the admin/includes directory
	 *
	 * @since 1.0.0
	 */
	public function load_includes() {
		require_once( 'includes/class-sunny-demo-option.php' );
		require_once( 'includes/class-sunny-demo-post-purger.php' );
		require_once( 'includes/class-sunny-demo-api-logger.php' );
		require_once( 'includes/class-sunny-demo-purger.php' );
	}
}

class-sunny-demo-api-logger.php

<?php
// sunny-demo/admin/includes/class-sunny-demo-api-logger.php

/**
 * Helper class. Log API responses.
 */
class Sunny_Demo_API_Logger {
	/**
	 * Log debug messages in php error log.
	 *
	 * @since     1.0.0
	 *
	 * @param     $response The response after api call, could be WP Error object or HTTP return object
	 * @param     $url      The Url that API calls
	 *
	 * @return    void      No return
	 */
	public static function write_report( $response, $url ) {

		if ( is_wp_error( $response ) ) {

			error_log( 'Sunny Demo ' . 'WP Error ' . $response->get_error_message() . $url );

		}// end WP Error

		else {

			// API made
			$response_array = json_decode( $response['body'], true );

			if ( 'error' == $response_array['result'] ) {

				error_log( 'Sunny Demo ' . 'API Error ' . $response_array['msg'] .'--' . $url );
				error_log( 'Sunny Demo ' . 'API Error ' . $response_array['msg'] .'--' . $url );


			} else {

				error_log( 'Sunny Demo' . 'API Success ' . $url );

			} // end else

		} // end API made

	} // end  write_report( $response, $url )

} // end Sunny_Demo_API_Logger 

class-sunny-demo-purger.php

<?php
// sunny-demo/admin/includes/class-sunny-demo-purger.php

Class Sunny_Demo_Purger {

	 // The URL of the API
	private static $CLOUDFLARE_API_ENDPOINT = 'https://www.cloudflare.com/api_json.html';

	/**
	 * Purge single file in CloudFlare's cache by making `zone_file_purge` calls
	 *
	 * @since    1.0.0
	 *
	 * @param    array    $url    Url to be purged
	 */
	public static function purge_cloudflare_cache_by_url( $url ) {

		$temp_domain = explode( '.', parse_url( esc_url_raw( $url ), PHP_URL_HOST ) );
    $domain = $temp_domain[count( $temp_domain )-2] . '.' . $temp_domain[count( $temp_domain )-1];

		$data = array(
      'email' => get_option( 'sunny_demo_cloudflare_email' ),
      'tkn'   => get_option( 'sunny_demo_cloudflare_api_key' ),
      'a'     => 'zone_file_purge',
      'z'     => $domain,
      'url'   => $url
      );

		$response = wp_remote_post(
		      self::$CLOUDFLARE_API_ENDPOINT,
		      array(
		        'body' => $data
		      )
		    );

		Sunny_Demo_API_Logger::write_report( $response, $url );

		return $response;

	} // end purge_cloudflare_cache_by_url

} // end Sunny_Demo_Purger

purge_post.php

<?php
// inside class Sunny_Demo_Post_Purger

/**
 * Purge the updated post only if it is published.
 * Hooked into 'save_post'
 *
 * @param     integer    $post_id    The current post being saved
 *
 * @since     1.0.0
 */
 public function purge_post( $post_id ) {

  if ( $this->should_purge( $post_id ) ) {
    
    $url = get_permalink( $post_id );
    Sunny_Demo_Purger::purge_cloudflare_cache_by_url( $url );

  }

  return $post_id;

} // end purge_post

/**
 * Verifies that the user who is currently logged in has permission to save the post
 * and the post is published.
 *
 * @since     1.0.0
 *
 * @param     integer    $post_id    The current post being saved.
 *
 * @return    boolean                True if the user can save the information
 */
private function should_purge( $post_id ) {

  $post = get_post( $post_id );

  if ( false == is_object( $post )  ) {

    return false;

  } // end if

  $is_autosave = wp_is_post_autosave( $post_id );
  $is_revision = wp_is_post_revision( $post_id );
  $is_published = ( 'publish' == get_post_status( $post_id ) );

  return ! ( $is_autosave || $is_revision ) && $is_published;

} //end should_purge

singleton.php

<?php
// sunny-demo/admin/includes/class-sunny-demo-post-purger.php

/**
 * This class takes care the purge process fired from the admin dashboard.
 */
class Sunny_Demo_Post_Purger {
	/**
	 * Instance of this class.
	 *
	 * @since    1.0.0
	 *
	 * @var      object
	 */
	protected static $instance = null;

	/**
	 * Initialize the class and purge after post saved
	 *
	 * @since     1.0.0
	 */
	private function __construct() {

	  add_action( 'save_post', array( $this, 'purge_post' ), 20 );

	}

	/**
	 * Return an instance of this class.
	 *
	 * @since     1.0.0
	 *
	 * @return    object    A single instance of this class.
	 */
	public static function get_instance() {
	  // If the single instance hasn't been set, set it now.
	  if ( null == self::$instance ) {
	    self::$instance = new self;
	  }
	  return self::$instance;
  }

}