How to include the Advanced Custom Fields plugin inside your own plugin.

index.php

<?php
// Define path and URL to the ACF plugin.
// Including in a theme uses get_stylesheet_directory on line 4, but for a plugin you need a different call.
// This is the correct way to call the ACF plugin inside a plugin
define( 'MY_ACF_PATH', plugin_dir_path( __FILE__ ) . '/includes/acf/' );
define( 'MY_ACF_URL', plugin_dir_url( __FILE__ ) . '/includes/acf/' );

// Include the ACF plugin.
include_once( MY_ACF_PATH . 'acf.php' );

// Customize the url setting to fix incorrect asset URLs.
add_filter('acf/settings/url', 'my_acf_settings_url');
function my_acf_settings_url( $url ) {
		return MY_ACF_URL;
}

// (Optional) Hide the ACF admin menu item.
add_filter('acf/settings/show_admin', 'my_acf_settings_show_admin');
function my_acf_settings_show_admin( $show_admin ) {
		return false;
}