How to access the WordPress DB from a plugin file

Question

If you plan to share/sell your plugin I strongly suggest don’t load your plugin directly.

That because to load WordPress you need to load the bootstrap file, that is /wp-load.php so, you should put in your embed-video.php something like:

require '/wordpress/path/wp-load.php';

Do you notice the problem here? The /wordpress/path/ part is different for user to user, and, really, even if you use something like

require dirname( dirname( dirname( dirname( __FILE__ ) ) ) ) . '/wp-load.php';

It’s not enough, because wp_content folder and/or plugins folder can be moved from standard position, so you can never be sure where they are.

If you are writing a plugin only for yourself, you can do it, because you know where your files are, just be sure to use a flexible manner to define the path, because even youcan need to move your folders in future.

If you are writing plugin to share/sell you’ll need to use an alternative.

One is to send requests to admin-ajax.php and use the ajax api. I know that you are thinking that your request is not ajax, but that’s not a problem: any ajax request is just an http request, so it will work even if you send a “normal” GET request.

Example code:

add_action( 'plugins_loaded', function() {
  /*
  once we use ajax api we can check if DOING_AJAX is set
  even if we are not really doing ajax
  that will reduce the times we perform code, speeding up you others requests
  */
  if ( ! defined('DOING_AJAX') ) return;

  /*
  check if the url contain the GET argument 'action' set to 'embedvideo'
  and contain the video id in the argument 'video'
  if not do nothing
  */
  $action = filter_input( INPUT_GET, 'action', FILTER_SANITIZE_STRING );
  $embed = (int) filter_input( INPUT_GET, 'video', FILTER_SANITIZE_NUMBER_INT );
  if ( $action === 'embed_video' || ! $embed > 0 ) return; 

  /* add the ajax action for logged and not logged users */
  add_action( "wp_ajax_{$action}", 'video_request'  );
  add_action( "wp_ajax_nopriv_{$action}", 'video_request'  );
});

Previous code add the action only when needed, speeding up all others requests, because 'plugins_loaded' hooks is fired for every request.

Now add the action function, where you’ll put the logic:

function video_request() {
   /* 
   check if the url contain a video id in the GET argument 'video' if not do nothing
   */
   $video = (int) filter_input( INPUT_GET, 'video', FILTER_VALIDATE_NUMBER_INT );
   if ( ! $video > 0 ) return;

   /* your post ID is in $video variable and you have WordPress available */
   $post = get_post( $video );

   // do stuff

   /*
   must exit(), because even not sended via ajax, we use ajax api that require to exit
   */
   exit(); 
}

Adding previous code to your plugin, you can use a function to easily generate the right urls:

function get_video_embed_url( $videoid = NULL ) {
  if ( is_numeric( $videoid ) && (int) $postid > 0 ) {
    $args = array( 'action' => 'embed_video', 'video' => $postid );
    return add_query_arg( $args, admin_url( 'admin_ajax.php' );
  }
  return '#';
}

function video_embed_url( $videoid = NULL ) {
  echo get_video_embed_url( $videoid );
}

After that, wherever you need the url video_embed_url( $id ) will echo the url (e.g. in html markup) get_video_embed_url( $id ) will return the url to use in code.

The urls will be something like

mysite.com/wp-admin/admin_ajax.php?action=embed_video&video={$videoid}

This code can seems more than you need, but:

it uses best practice, and allow you to share/sell your plugin
it’s developed using ajax api, and even if now you aren’t using ajax, in future you can mind to use it, and in that case you have to do nothing: your plugin is ready

A trick: use it with caution, or not use it at all

As said, when write code only for yourself, you can think to directly load your plugin file. And I also said that is better use a flexible way to defined paths.
This is an example of how you can flexible define them: not define at all, but pass in the url:

/* in main plugin file, that I suppose to be in the same folder of embed-video.php */
function my_embed_url( $id ) {
  if ( is_numeric( $id ) && $id > 0 ) {
    $base = plugins_url( '/embed-video.php', __FILE__ );
    $path = urlencode( base64_encode( trailingslashit( ABSTPATH ) . 'wp-load.php' ) );
    return add_aquery_arg( array( 'path' => $path, 'video' => $id ), $base );
  }
}

Previous function will return something like mysite.com/wp-content/plugins/myplugin/embed-video.php?path=L3Zhci93d3cvd29yZHByZXNzL3dwLWxvYWQucGhw&video=123 use this function to output the embed video (if you need to use url in post content use a shortcode).

Doing so, in first lines of embed-video.php you can:

$raw = filter_input( INPUT_GET, 'path', FILTER_SANITIZE_STRING );
$videoid = (int) filter_input( INPUT_GET, 'video', FILTER_SANITIZE_NUMBER_INT );
if ( empty($raw) || empty($videoid) || ! $videoid > 0 ) exit();
$path =  urldecode( base64_decode( $raw ) );
if ( ! file_exists( $path ) ) exit();

define( 'SHORTINIT', 1 ); // this allow you to load only minimun WP environment
require_once $path;

/* WordPress is available */
$post = get_post( $videoid );

A trick: use it with caution, or not use it at all

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