How to include WordPress functions in custom .php file?

Question

How can I include WordPress functions in a custom .php file?

In detail: I have a directory under my theme (Constructor) named reports. These contain .php files that generate reports from data from the site with DOMPDF for downloading. For these I would like to use functions that the WordPress engine provides, for example get_the_author_meta( 'user_firstname', $user_id ). If I use these i get (naturally) the following error:

Fatal error: Call to undefined function get_the_author_meta() in ROOT/public_html/wp-content/themes/constructor/reports/testreport.php on line 15

I was lead to believe that I need to include wp-blog-header.php . I use require_once("../../../../wp-blog-header.php"); . With this I get the following 404 error:

No webpage was found for the web address: ROOT/wp-content/themes/constructor/reports/testreport.php

(The require points to the correct path. If I fiddle with it, I get Warning: require_once(../../../wp-blog-header.php): failed to open stream... So the path must be correct.)

Is there something I overlook? Why can't I include this wp file? What is the correct method to include the wp functions?

Thanks for the help, Sziro

Answer 1

You're on the right track. Try this instead:

require_once("../../../../wp-load.php");

Answer 2

To use wp functions in custom .php files, you must include wp-load.php in your file. You can do so by adding the following line:

require_once(PATH_TO.'/wp-load.php');

If WordPress is in the document root add instead:

require_once($_SERVER['DOCUMENT_ROOT'].'/wp-load.php');

Answer 3

Well if someone has newer PHP versions installed (ver >= 5.5.x) then they can also try the below code in the root script in WordPress website directory itself:

<?php
define("WP_ROOT", __DIR__);
define("DS", DIRECTORY_SEPARATOR);
require_once WP_ROOT . DS . "wp-load.php";

Or

<?php
define("WP_ROOT", __DIR__);
define("DS", DIRECTORY_SEPARATOR);
require_once WP_ROOT . DS . "wp-blog-header.php";

I guess this is a more direct and clean approach and doesn't involve manually adding slashes and changing diretories by ...

Hope this helps someone.