Title: function is_plugin_active() Last modified: December 2, 2019 --- # function is_plugin_active() * Resolved [Hannes Etzelstorfer](https://wordpress.org/support/users/haet/) * (@haet) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/) * Hello, I just tried to install the plugin on a multisite installation and for some reason there has been an conflict with Klaviyo for WooCommerce. I had a look at the code of both plugins and could fix the problem by replacing your check for active WooCommerce and active Pro-Version by the function is_plugin_active(). In my opinion the statements used before were absolutely correct, I just wanted to simplify the code and solved the conflict “by mistake” 😉 Here are the new first lines in left-to-free-shipping-for-woocommerce.php: * ``` if ( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly // Check if WooCommerce is active if ( !is_plugin_active('woocommerce/woocommerce.php') ) { return; } if ( 'left-to-free-shipping-for-woocommerce.php' === basename( __FILE__ ) ) { // Check if Pro is active, if so then return if ( is_plugin_active( 'left-to-free-shipping-for-woocommerce-pro/left-to-free-shipping-for-woocommerce-pro.php' ) ) { return; } } if ( ! class_exists( 'Alg_WC_Left_To_Free_Shipping' ) ) : ``` Viewing 9 replies - 1 through 9 (of 9 total) * Plugin Author [Algoritmika](https://wordpress.org/support/users/algoritmika/) * (@algoritmika) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12196470) * Hi [@haet](https://wordpress.org/support/users/haet/), * Thanks for the `is_plugin_active()`, really appreciate it. To be honest, I didn’t know about this function. Will have to change it in all my plugins now :/ Not sure what could cause the compatibility issue with the old code though… * Plugin Author [Algoritmika](https://wordpress.org/support/users/algoritmika/) * (@algoritmika) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12196696) * Hi again, [@haet](https://wordpress.org/support/users/haet/), * I’ve tried it out and now I remembered that I actually already tried using `is_plugin_active()`– it produces `Call to undefined function is_plugin_active()` error on my server. The problem that this function is only defined in `wp-admin/includes/plugin.php` file, which loads later. So basically `is_plugin_active()` should be used in ` admin_init` hook for example. In your case, I assume, some other plugin is requiring` wp-admin/includes/plugin.php` file earlier, which I’m not sure is a good idea. Anyway, I think I found a solution that should work on all servers – it will be added in next plugin version. * Thread Starter [Hannes Etzelstorfer](https://wordpress.org/support/users/haet/) * (@haet) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12196865) * You could / should wrap your initialization code in * ``` add_action( 'plugins_loaded', function(){ // your init code here }); ``` * so you can make sure the WordPress core is initialized. * Plugin Author [Algoritmika](https://wordpress.org/support/users/algoritmika/) * (@algoritmika) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12196934) * [@haet](https://wordpress.org/support/users/haet/), * Yes, I’ve also thought of `plugins_loaded` hook. * Thread Starter [Hannes Etzelstorfer](https://wordpress.org/support/users/haet/) * (@haet) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12196950) * Thanks for the fast reply! * Plugin Author [Algoritmika](https://wordpress.org/support/users/algoritmika/) * (@algoritmika) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12203907) * Hi [@haet](https://wordpress.org/support/users/haet/), * I’ve just tried it with `plugins_loaded`, but it looks like `is_plugin_active()` is still not defined yet. The only hook that I found which has this function already defined is `admin_init`. Also it looks like it’s available in admin only– I’ve tried it in `init` hook and it’s not defined there. * So I’m thinking about defining my own function: * ``` /* * alg_is_plugin_active. */ function alg_is_plugin_active( $plugin ) { return ( function_exists( 'is_plugin_active' ) ? is_plugin_active( $plugin ) : ( in_array( $plugin, apply_filters( 'active_plugins', (array) get_option( 'active_plugins', array() ) ) ) || ( is_multisite() && array_key_exists( $plugin, (array) get_site_option( 'active_sitewide_plugins', array() ) ) ) ) ); } ``` * So basically I’m using `is_plugin_active()` if it’s already defined (like in your case) and otherwise I’m using my own code (which is basically same code copied from `is_plugin_active()` source). This should solve the issue on your server. Still not sure why your server doesn’t like my old code though – it’s basically the same code as in original WP. * Plugin Author [Algoritmika](https://wordpress.org/support/users/algoritmika/) * (@algoritmika) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12203982) * P.S. The only difference I’m seeing in the original WP code and my code is that I’m applying `active_plugins` filter on `get_option( 'active_plugins', array())`. I’ve copied this filter from WooCommerce – in `class-wc-helper.php` file: * ``` $active_plugins = apply_filters( 'active_plugins', get_option( 'active_plugins' ) ); ``` * Plugin Author [Algoritmika](https://wordpress.org/support/users/algoritmika/) * (@algoritmika) * [6 years, 6 months ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12204026) * P.P.S. I’ve just released new plugin v1.4.1 with the updated code as described above. * [SoN9ne](https://wordpress.org/support/users/son9ne/) * (@son9ne) * [6 years, 1 month ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12674028) * FYI, it would be better practice to use: * ``` // Include file if function does not exist if (!function_exists('is_plugin_active')) { include_once(ABSPATH . 'wp-admin/includes/plugin.php'); } ``` * Other than making your own. Sure it works but be careful with copying from core, especially if they change how that works. Minor issue but worth mentioning. Viewing 9 replies - 1 through 9 (of 9 total) The topic ‘function is_plugin_active()’ is closed to new replies. * ![](https://s.w.org/plugins/geopattern-icon/amount-left-free-shipping-woocommerce_bfd7ef. svg) * [Free Shipping Bar: Amount Left for Free Shipping for WooCommerce](https://wordpress.org/plugins/amount-left-free-shipping-woocommerce/) * [Frequently Asked Questions](https://wordpress.org/plugins/amount-left-free-shipping-woocommerce/#faq) * [Support Threads](https://wordpress.org/support/plugin/amount-left-free-shipping-woocommerce/) * [Active Topics](https://wordpress.org/support/plugin/amount-left-free-shipping-woocommerce/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/amount-left-free-shipping-woocommerce/unresolved/) * [Reviews](https://wordpress.org/support/plugin/amount-left-free-shipping-woocommerce/reviews/) * 9 replies * 3 participants * Last reply from: [SoN9ne](https://wordpress.org/support/users/son9ne/) * Last activity: [6 years, 1 month ago](https://wordpress.org/support/topic/function-is_plugin_active/#post-12674028) * Status: resolved