Check if plugin exists/active "class_exists()" does not work on plugin territory

Question

I have a simple if statement:

if (class_exists('Woocommerce')) {
    echo 'yes';
 } else {
    echo 'no';
}

This works fine when using it in a theme file (functions.php for example). But when I'm using it on a plugin (plugins/myplugin/myplugin.php) it doesn't work at all. How can I check if the plugin exists/is-active within my plugin to enable/disable some features? Am I missing something?

Answer 1

Woo Commerce provides code to check to see if WooCommerce is installed :

/**
 * Check if WooCommerce is active
 **/
if ( in_array( 'woocommerce/woocommerce.php', apply_filters( 'active_plugins', get_option( 'active_plugins' ) ) ) ) {
    // Put your plugin code here
}

If no idea where WooCommerece install then :

    $all_plugins = get_plugins();
    $active_plugins = get_option( "active_plugins" );

    foreach ( $all_plugins as $plugin_path => $value ) {

        if( basename( $plugin_path, ".php" ) == 'woocommerce') {
            if( in_array( $plugin_path, $active_plugins ) ) {
                return true;
            }else {
                return false;
            }
        }
    }

Answer 2

The best way is to run your code at actions triggered by the other plugin. If it has some initialization action than it is a perfect solution.

Otherwise this kind of check should better be done on the core wp_loaded hook and for sure not before plugins_loaded hook. Running it directly without any dependence on hook will just never work reliably.