Multiple files in a plugin

Question

I'm trying to write a plugin with multiple files. I'm sure I did it before without a problem, but now I have the problem in the subject.

In the main plugin file I have included a file name - ydp-includes.php. Inside of ydp-includes.php I have included all the files I wanted like this:

<?php
include(dirname( __FILE__ ) .'/1.php');
include(dirname( __FILE__ ) .'/2.php');
include(dirname( __FILE__ ) .'/3.php');
include(dirname( __FILE__ ) .'/4.php');
?>

but I'm getting:

Fatal error: Call to undefined function add_action().

The files are included, but for a reason I can't see at the moment, WordPress doesn't see them as one plugin package and each WordPress function inside ignored.

Is there another best practice way to develop multiple files WordPress plugin? What am I doing wrong?

Answer 1

This happens only if you call a file per HTTP without loading WordPress. That is something you should never do, because the plugin URL might be another domains where cookies don’t work anymore.

Answer 2

I generally have just one PHP file in the plugin folder, then a sub-folder within which all my required PHP files sit. I use the following code in the main file to automatically include all files found in the inc directory:

foreach ( glob( dirname( __FILE__ ) . '/inc/*.php' ) as $file ) {
    require $file;
}

Answer 3

Try this

<?php
include( plugin_dir_path( __FILE__ ) . '/1.php');
include( plugin_dir_path( __FILE__ ) . '/2.php');
include( plugin_dir_path( __FILE__ ) . '/3.php');
include( plugin_dir_path( __FILE__ ) . '/4.php');
?>