WordPress Virtual page with theme

class-virtualthemedpage-bc.php

<?php
/*
 * Virtual Themed Page class
 *
 * This class implements virtual pages for a plugin.
 *
 * It is designed to be included then called for each part of the plugin
 * that wants virtual pages.
 *
 * It supports multiple virtual pages and content generation functions.
 * The content functions are only called if a page matches.
 *
 * The class uses the theme templates and as far as I know is unique in that.
 * It also uses child theme templates ahead of main theme templates.
 *
 * Example code follows class.
 *
 * August 2013 Brian Coogan
 *
 */




// There are several virtual page classes, we want to avoid a clash!
//
//
class Virtual_Themed_Pages_BC
{
    public $title = '';
    public $body = '';
    private $vpages = array();  // the main array of virtual pages
    private $mypath = '';
    public $blankcomments = "blank-comments.php";


    function __construct($plugin_path = null, $blankcomments = null)
    {
	if (empty($plugin_path))
	    $plugin_path = dirname(__FILE__);
	$this->mypath = $plugin_path;

	if (! empty($blankcomments))
	    $this->blankcomments = $blankcomments;

	// Virtual pages are checked in the 'parse_request' filter.
	// This action starts everything off if we are a virtual page
	add_action('parse_request', array(&$this, 'vtp_parse_request'));
    }

    function add($virtual_regexp, $contentfunction)
    {
	$this->vpages[$virtual_regexp] = $contentfunction;
    }


    // Check page requests for Virtual pages
    // If we have one, call the appropriate content generation function
    //
    function vtp_parse_request(&$wp)
    {
	//global $wp;
	if (empty($wp->query_vars['pagename']))
	    return; // page isn't permalink

	//$p = $wp->query_vars['pagename'];
	$p = $_SERVER['REQUEST_URI'];

	$matched = 0;
	foreach ($this->vpages as $regexp => $func)
	{
	    if (preg_match($regexp, $p))
	    {
		$matched = 1;
		break;
	    }
	}
	// Do nothing if not matched
	if (! $matched)
	    return;

	// setup hooks and filters to generate virtual movie page
	add_action('template_redirect', array(&$this, 'template_redir'));
	add_filter('the_posts', array(&$this, 'vtp_createdummypost'));
	
	// we also force comments removal; a comments box at the footer of
	// a page is rather meaningless.
	// This requires the blank_comments.php file be provided
	add_filter('comments_template', array(&$this, 'disable_comments'), 11);

	// Call user content generation function
	// Called last so it can remove any filters it doesn't like
	// It should set:
	//    $this->body   -- body of the virtual page
	//    $this->title  -- title of the virtual page
	//    $this->template  -- optional theme-provided template
	//          eg: page
	//    $this->subtemplate -- optional subtemplate (eg movie)
	// Doco is unclear whether call by reference works for call_user_func()
	// so using call_user_func_array() instead, where it's mentioned.
	// See end of file for example code.
	$this->template = $this->subtemplate = null;
	$this->title = null;
	unset($this->body);
	call_user_func_array($func, array(&$this, $p));

	if (! isset($this->body)) //assert
	    wp_die("Virtual Themed Pages: must save ->body [VTP07]");

	return($wp);
    }


    // Setup a dummy post/page 
    // From the WP view, a post == a page
    //
    function vtp_createdummypost($posts)
    {

	// have to create a dummy post as otherwise many templates
	// don't call the_content filter
	global $wp, $wp_query;

	//create a fake post intance
	$p = new stdClass;
	// fill $p with everything a page in the database would have
	$p->ID = -1;
	$p->post_author = 1;
	$p->post_date = current_time('mysql');
	$p->post_date_gmt =  current_time('mysql', $gmt = 1);
	$p->post_content = $this->body;
	$p->post_title = $this->title;
	$p->post_excerpt = '';
	$p->post_status = 'publish';
	$p->ping_status = 'closed';
	$p->post_password = '';
	$p->post_name = 'movie_details'; // slug
	$p->to_ping = '';
	$p->pinged = '';
	$p->modified = $p->post_date;
	$p->modified_gmt = $p->post_date_gmt;
	$p->post_content_filtered = '';
	$p->post_parent = 0;
	$p->guid = get_home_url('/' . $p->post_name); // use url instead?
	$p->menu_order = 0;
	$p->post_type = 'page';
	$p->post_mime_type = '';
	$p->comment_status = 'closed';
	$p->comment_count = 0;
	$p->filter = 'raw';
	$p->ancestors = array(); // 3.6

	// reset wp_query properties to simulate a found page
	$wp_query->is_page = TRUE;
	$wp_query->is_singular = TRUE;
	$wp_query->is_home = FALSE;
	$wp_query->is_archive = FALSE;
	$wp_query->is_category = FALSE;
	unset($wp_query->query['error']);
	$wp->query = array();
	$wp_query->query_vars['error'] = '';
	$wp_query->is_404 = FALSE;

	$wp_query->current_post = $p->ID;
	$wp_query->found_posts = 1;
	$wp_query->post_count = 1;
	$wp_query->comment_count = 0;
	// -1 for current_comment displays comment if not logged in!
	$wp_query->current_comment = null;
	$wp_query->is_singular = 1;

	$wp_query->post = $p;
	$wp_query->posts = array($p);
	$wp_query->queried_object = $p;
	$wp_query->queried_object_id = $p->ID;
	$wp_query->current_post = $p->ID;
	$wp_query->post_count = 1;

	return array($p);
    }


    // Virtual Movie page - tell wordpress we are using the given
    // template if it exists; otherwise we fall back to page.php.
    //
    // This func gets called before any output to browser
    // and exits at completion.
    //
    function template_redir()
    {
	//    $this->body   -- body of the virtual page
	//    $this->title  -- title of the virtual page
	//    $this->template  -- optional theme-provided template eg: 'page'
	//    $this->subtemplate -- optional subtemplate (eg movie)
	//

	if (! empty($this->template) && ! empty($this->subtemplate))
	{
	    // looks for in child first, then master:
	    //    template-subtemplate.php, template.php
	    get_template_part($this->template, $this->subtemplate);
	}
	elseif (! empty($this->template))
	{
	    // looks for in child, then master:
	    //    template.php
	    get_template_part($this->template);
	}
	elseif (! empty($this->subtemplate))
	{
	    // looks for in child, then master:
	    //    template.php
	    get_template_part($this->subtemplate);
	}
	else
	{
	    get_template_part('page');
	}

	// It would be possible to add a filter for the 'the_content' filter
	// to detect that the body had been correctly output, and then to
	// die if not -- this would help a lot with error diagnosis.

        exit;
    }


    // Some templates always include comments regardless, sigh.
    // This replaces the path of the original comments template with a
    // empty template file which returns nothing, thus eliminating
    // comments reliably.
    function disable_comments($file)
    {
	if (file_exists($this->blankcomments))
	   return($this->mypath.'/'.$blankcomments);
	return($file);
    }


} // class


// Example code - you'd use something very like this in a plugin
//
if (0)
{
    // require 'BC_Virtual_Themed_pages.php';
    // this code segment requires the WordPress environment

    $vp =  new Virtual_Themed_Pages_BC();
    $vp->add('#/mypattern/unique#i', 'mytest_contentfunc');
    
    // Example of content generating function
    // Must set $this->body even if empty string
    function mytest_contentfunc($v, $url)
    {
	// extract an id from the URL
	$id = 'none';
	if (preg_match('#unique/(\d+)#', $url, $m))
	    $id = $m[1];
	// could wp_die() if id not extracted successfully...

	$v->title = "My Virtual Page Title";
	$v->body = "Some body content for my virtual page test - id $id\n";
	$v->template = 'page'; // optional
	$v->subtemplate = 'billing'; // optional
    }
}




// end

Has anyone been able to get this to work on Wordpress 6.1.1 (or newer once that happens)? I get a couple of errors that look like "Trying to get property 'post_type' of non-object in .../wp-includes/link-template.php on line 4066." If I downgrade to Wordpress 6.0.3 then I can my code working.

Update: Looks like this person figured it out: https://stackoverflow.com/questions/74613027/wordpress-virtual-page-trying-to-get-property-post-type-of-non-object

Also, here is another plugin that could be helpful to the next person!
https://gist.github.com/gmazzap/1efe17a8cb573e19c086

This is such a handy bit of code, I've been really pleased with how it works, but naturally at the eleventh hour I've realised I have a problem.

If the path has multiple slashes in it, the page works fine, but it's returned with a 404 status. So /catalogue/?product_id=123 is fine as is /catalogue/?search=foo however where I have pages like /catalogue/widgets/my_super_widget/ while displaying correctly, they are returned as a 404 error page.

Has anyone else got any pointers on how to sort this out, please?

This is such a handy bit of code, I've been really pleased with how it works, but naturally at the eleventh hour I've realised I have a problem.

If the path has multiple slashes in it, the page works fine, but it's returned with a 404 status. So /catalogue/?product_id=123 is fine as is /catalogue/?search=foo however where I have pages like /catalogue/widgets/my_super_widget/ while displaying correctly, they are returned as a 404 error page.

Has anyone else got any pointers on how to sort this out, please?

@tobestool Sorry for the late reply. I just discovered this issue myself. I believe it was caused by a wordpress update. Anyway, if you add the following line to dummypost, it should rid the 404

$wp->query_vars['error']='';