4 Trees - WordPress check if plugin is active

/**
 * check if a plugin is active ##
 */
if ( !function_exists( 'ftf_plugin_is_active' ) ) {
function ftf_plugin_is_active( $plugin ) {
    return in_array( $plugin, (array) get_option( 'active_plugins', array() ) );
}}

// example usage ##
if ( ftf_plugin_is_active( 'mailchimp/mailchimp.php' ) ) {
    // do stuff ##
}