Before running any code that modifies the behavior of Inventory Presser, make sure Inventory Presser is active. Check if the INVP class exists.

Plugins are not loaded until after the plugins_loaded hook.

Check if Inventory Presser is Active

<?php
if ( class_exists( 'INVP' ) ) {
	//Inventory Presser is active
}

Check if Inventory Presser is Not Active

<?php
if ( ! class_exists( 'INVP' ) ) {
	//Inventory Presser is not active
}

Action Hook After Inventory Presser Loads

The action hook invp_loaded is run after Inventory Presser has completely loaded. This hook is useful to make sure add-on plugins do not load earlier than the core plugin.

<?php
	add_action( 'invp_loaded', array( 'My_Addon_Loader', 'load' ) );
	class My_Addon_Loader {
		public static function load() {
			require_once( __DIR__ . '/includes/class-addon.php' );
			$addon = new My_Addon();
			$addon->add_hooks();
		}
	}