Can the wp-plugins (Must Use Plugins) URL be targeted for use in functions.php?

Can the wp-plugins (Must Use Plugins) URL be targeted for use in functions.php? I have a mu-functions.php file in the mu-plugins folder. One function calls a javascript file (alerts.js) located in example/wp-content/mu-plugins/js/. How can I target the mu-plugins folder in my function?

Currently, I am using get_site_url() . '/wp-content/mu-plugins/js/alerts.js',

Although not completely relevant to the question, this is the complete function used to call the javascript file:

function load_my_alerts(){
      wp_register_script( 
        'my_alerts', 
        get_site_url() . '/wp-content/mu-plugins/js/alerts.js', 
        array( 'jquery' )
    );
    wp_enqueue_script( 'my_alerts' );
}
add_action('admin_enqueue_scripts', 'load_my_alerts');

Can the wp-plugins (Must Use Plugins) URL be targeted for use in functions.php? I have a mu-functions.php file in the mu-plugins folder. One function calls a javascript file (alerts.js) located in example/wp-content/mu-plugins/js/. How can I target the mu-plugins folder in my function?

Currently, I am using get_site_url() . '/wp-content/mu-plugins/js/alerts.js',

Although not completely relevant to the question, this is the complete function used to call the javascript file:

function load_my_alerts(){
      wp_register_script( 
        'my_alerts', 
        get_site_url() . '/wp-content/mu-plugins/js/alerts.js', 
        array( 'jquery' )
    );
    wp_enqueue_script( 'my_alerts' );
}
add_action('admin_enqueue_scripts', 'load_my_alerts');

• functions
• mu-plugins

Share Improve this question asked Jan 7, 2013 at 22:50 Travis PflanzTravis Pflanz 1,95355 gold badges3131 silver badges5757 bronze badges

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4 Answers 4

Sorted by: Reset to default 3

EDIT: this solution is not a best-practice. Please use the solution submitted by Nathan below!

Use the WPMU_PLUGIN_DIR and WPMU_PLUGIN_URL constants :)

function load_my_alerts(){
    wp_register_script( 
        'my_alerts', 
        WPMU_PLUGIN_URL . '/js/alerts.js', 
        array( 'jquery' )
    );
    wp_enqueue_script( 'my_alerts' );
}
add_action('admin_enqueue_scripts', 'load_my_alerts');

FYI, Nathan's example only works for regular plugins, not "Must Use Plugins". To make it work for MU plugins, you need to pass the invoking file:

plugins_url('/path/to/whatever', __FILE__)

It is not good practice to use constants. For this functionality one should ALWAYS use the plugins_url() function seen here in the codex.

    function load_my_alerts(){

        wp_register_script(
            'my_alerts',
            plugins_url('js/alerts.js'),
            array( 'jquery' )
        );

        wp_enqueue_script( 'my_alerts' );

    }

    add_action('admin_enqueue_scripts', 'load_my_alerts');

When using plugins_url() outside of an mu-plugin, you need to specify the full path to the plugin that is in the mu-plugins directory. For example, when using it in a theme's functions.php file.

Below is a correct working version, where the second parameter of plugins_url() is a full path to the plugin in the mu-plugins directory.

Please see the codex for more info.

function load_my_plugin_script(){

    wp_register_script(
        'my_plugin_script',
        plugins_url('my_plugin.js', '/wp/wp-content/mu-plugins/my_plugin')
    );

    wp_enqueue_script( 'my_plugin_script' );

}

add_action('admin_enqueue_scripts', 'load_my_plugin_script');