WordPress plugin to ease the creation of virtual pages.

Controller.php

<?php
namespace GM\VirtualPages;

/**
 * @author  Giuseppe Mazzapica <giuseppe.mazzapica@gmail.com>
 * @license http://opensource.org/licenses/MIT MIT
 */
class Controller implements ControllerInterface {

  private $pages;
  private $loader;
  private $matched;
  
  function __construct( TemplateLoaderInterface $loader ) {
    $this->pages = new \SplObjectStorage;
    $this->loader = $loader;
  }
  
  function init() {
    do_action( 'gm_virtual_pages', $this ); 
  }
  
  function addPage( PageInterface $page ) {
    $this->pages->attach( $page );
    return $page;
  }
  
  function dispatch( $bool, \WP $wp ) {
    if ( $this->checkRequest() && $this->matched instanceof Page ) {
      $this->loader->init( $this->matched );
      $wp->virtual_page = $this->matched;
      do_action( 'parse_request', $wp );
      $this->setupQuery();
      do_action( 'wp', $wp );
      $this->loader->load();
      $this->handleExit();
    }
    return $bool;
  }
  
  private function checkRequest() {
    $this->pages->rewind();
    $path = trim( $this->getPathInfo(), '/' );
    while( $this->pages->valid() ) {
      if ( trim( $this->pages->current()->getUrl(), '/' ) === $path ) {
        $this->matched = $this->pages->current();
        return TRUE;
      }
      $this->pages->next();
    }
  }        
  
  private function getPathInfo() {
    $home_path = parse_url( home_url(), PHP_URL_PATH );
    return preg_replace( "#^/?{$home_path}/#", '/', add_query_arg( array() ) );
  }
  
  private function setupQuery() {
    global $wp_query;
    $wp_query->init();
    $wp_query->is_page       = TRUE;
    $wp_query->is_singular   = TRUE;
    $wp_query->is_home       = FALSE;
    $wp_query->found_posts   = 1;
    $wp_query->post_count    = 1;
    $wp_query->max_num_pages = 1;
    $posts = (array) apply_filters(
      'the_posts', array( $this->matched->asWpPost() ), $wp_query
    );
    $post = $posts[0];
    $wp_query->posts          = $posts;
    $wp_query->post           = $post;
    $wp_query->queried_object = $post;
    $GLOBALS['post']          = $post;
    $wp_query->virtual_page   = $post instanceof \WP_Post && isset( $post->is_virtual )
      ? $this->matched
      : NULL;
  }
  
  public function handleExit() {
    exit();
  }
}

ControllerInterface.php

<?php
namespace GM\VirtualPages;

/**
 * @author  Giuseppe Mazzapica <giuseppe.mazzapica@gmail.com>
 * @license http://opensource.org/licenses/MIT MIT
 */
interface ControllerInterface {

  /**
   * Init the controller, fires the hook that allow consumer to add pages
   */
  function init();
  
  /**
   * Register a page object in the controller
   *
   * @param  \GM\VirtualPages\Page $page
   * @return \GM\VirtualPages\Page
   */
  function addPage( PageInterface $page );
  
  /**
   * Run on 'do_parse_request' and if the request is for one of the registerd
   * setup global variables, fire core hooks, requires page template and exit.
   *
   * @param boolean $bool The boolean flag value passed by 'do_parse_request'
   * @param \WP $wp       The global wp object passed by 'do_parse_request'
   */  
  function dispatch( $bool, \WP $wp );
  
}

gm-virtual-pages.php

<?php namespace GM\VirtualPages;
/*
Plugin Name: GM Virtual Pages
Plugin URI: http://wordpress.stackexchange.com/questions/162240/custom-pages-with-plugin
Description: Virtual pages made easy.
Author: Giuseppe Mazzapica
Author URI: http://gm.zoomlab.it
License: MIT
*/
 
require_once 'PageInterface.php';
require_once 'ControllerInterface.php';
require_once 'TemplateLoaderInterface.php';
require_once 'Page.php';
require_once 'Controller.php';
require_once 'TemplateLoader.php';

$controller = new Controller ( new TemplateLoader );

add_action( 'init', array( $controller, 'init' ) );

add_filter( 'do_parse_request', array( $controller, 'dispatch' ), PHP_INT_MAX, 2 );

add_action( 'loop_end', function( \WP_Query $query ) {
  if ( isset( $query->virtual_page ) && ! empty( $query->virtual_page ) ) {
    $query->virtual_page = NULL;
  }
} );

add_filter( 'the_permalink', function( $plink ) {
  global $post, $wp_query;
  if (
    $wp_query->is_page
    && isset( $wp_query->virtual_page )
    && $wp_query->virtual_page instanceof Page
    && isset( $post->is_virtual )
    && $post->is_virtual
  ) {
    $plink = home_url( $wp_query->virtual_page->getUrl() );
  }
  return $plink;
} );

LICENSE

The MIT License (MIT)

Copyright (c) 2016 Giuseppe Mazzapica

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Page.php

<?php
namespace GM\VirtualPages;

/**
 * @author  Giuseppe Mazzapica <giuseppe.mazzapica@gmail.com>
 * @license http://opensource.org/licenses/MIT MIT
 */
class Page implements PageInterface {

  private $url;
  private $title;
  private $content;
  private $template;
  private $wp_post;
  
  function __construct( $url, $title = 'Untitled', $template = 'page.php' ) {
    $this->url = filter_var( $url, FILTER_SANITIZE_URL );
    $this->setTitle( $title );
    $this->setTemplate( $template);
  }
  
  function getUrl() {
    return $this->url;
  }
  
  function getTemplate() {
    return $this->template;
  }
  
  function getTitle() {
    return $this->title;
  }
  
  function setTitle( $title ) {
    $this->title = filter_var( $title, FILTER_SANITIZE_STRING );
    return $this;
  }
  
  function setContent( $content ) {
    $this->content = $content;
    return $this;
  }
  
  function setTemplate( $template ) {
    $this->template = $template;
    return $this;
  }
  
  function asWpPost() {
    if ( is_null( $this->wp_post ) ) {
      $post = array(
        'ID'             => 0,
        'post_title'     => $this->title,
        'post_name'      => sanitize_title( $this->title ),
        'post_content'   => $this->content ? : '',
        'post_excerpt'   => '',
        'post_parent'    => 0,
        'menu_order'     => 0,
        'post_type'      => 'page',
        'post_status'    => 'publish',
        'comment_status' => 'closed',
        'ping_status'    => 'closed',
        'comment_count'  => 0,
        'post_password'  => '',
        'to_ping'        => '',
        'pinged'         => '',
        'guid'           => home_url( $this->getUrl() ),
        'post_date'      => current_time( 'mysql' ),
        'post_date_gmt'  => current_time( 'mysql', 1 ),
        'post_author'    => is_user_logged_in() ? get_current_user_id() : 0,
        'is_virtual'     => TRUE,
        'filter'         => 'raw'
      );
      $this->wp_post = new \WP_Post( (object) $post );
    }
    return $this->wp_post;
  }
}

PageInterface.php

<?php
namespace GM\VirtualPages;

/**
 * @author  Giuseppe Mazzapica <giuseppe.mazzapica@gmail.com>
 * @license http://opensource.org/licenses/MIT MIT
 */
interface PageInterface {

  function getUrl();
  
  function getTemplate();
  
  function getTitle();
  
  function setTitle( $title );
  
  function setContent( $content );
  
  function setTemplate( $template );
  
  /**
  * Get a WP_Post build using viryual Page object
  *
  * @return \WP_Post
  */
  function asWpPost();
}

TemplateLoader.php

<?php
namespace GM\VirtualPages;

/**
 * @author  Giuseppe Mazzapica <giuseppe.mazzapica@gmail.com>
 * @license http://opensource.org/licenses/MIT MIT
 */
class TemplateLoader implements TemplateLoaderInterface {

  public function init( PageInterface $page ) {
    $this->templates = wp_parse_args(
      array( 'page.php', 'index.php' ), (array) $page->getTemplate()
    );
  }
  
  public function load() {
    do_action( 'template_redirect' );
    $template = locate_template( array_filter( $this->templates ) );
    $filtered = apply_filters( 'template_include',
      apply_filters( 'virtual_page_template', $template )
    );
    if ( empty( $filtered ) || file_exists( $filtered ) ) {
      $template = $filtered;
    }
    if ( ! empty( $template ) &&file_exists( $template ) ) {
      require_once $template;
    }
  }
}

TemplateLoaderInterface.php

<?php
namespace GM\VirtualPages;

/**
 * @author  Giuseppe Mazzapica <giuseppe.mazzapica@gmail.com>
 * @license http://opensource.org/licenses/MIT MIT
 */
interface TemplateLoaderInterface {

  /**
  * Setup loader for a page objects
  *
  * @param \GM\VirtualPagesPageInterface $page matched virtual page
  */
  public function init( PageInterface $page );
  
  /**
  * Trigger core and custom hooks to filter templates,
  * then load the found template.
  */
  public function load();
}