Load js/css files only on specific admin UI pages

Question

How do I adapt this solution to work with my plugin? (Please see the link).

I enqueue my css and js script as follows:

function my_plugin_init() {
 wp_enqueue_script('my_plugin_script', plugins_url('js/the_filepath.js', __FILE__), array('jquery'));
 wp_enqueue_style( 'my_plugin_css', plugins_url( '/css/the_filepath.css', __FILE__ ) );
}

add_action('init', 'my_plugin_init');

I tried putting this in the theme's functions.php, but it didn't work:

function remove_my_plugin_extras() {
    remove_action('init', 'my_plugin_init');
}

if( !is_page('My_Page') ) {
    add_action('wp_head', 'remove_my_plugin_extras');
}

The script and css still loaded. How do I adapt the solution in this case?

Answer 1

The right hooks

    // Use both for scripts & styles *)
    wp_enqueue_scripts // (for the frontend)
    login_enqueue_scripts // (for the login screen)
    admin_enqueue_scripts // (for the admin dashboard)

^{*) Read this article @wpdevel.}

Further reading in the Codex about the three hooks

• admin_menu
• network_admin_menu
• user_admin_menu

On the admin_enqueue_scripts hook, you have an argument as well: The $hook_suffix:

add_action( 'admin_enqueue_scripts', function( $hook )
{
    var_dump( $hook );
} );

Admin page hooks

When registering a admin (sub)menu page, you can save the result, which is the page hook, into a variable:

function register_admin_page()
{
    // Register (sub)menu page
    $hook_suffix = add_submenu_page( $your_args_array );
    // Add styles to hook
    add_action( "load-{$hook_suffix}", 'callback_function' );
}
// Use one of those hooks to register the page
add_action( 'admin_menu', 'register_admin_page' );
add_action( 'user_admin_menu', 'register_admin_page' );
add_action( 'network_admin_menu', 'register_admin_page' );

// Register your styles & scripts in here
function callback_function()
{
    // do stuff
}

Admin globally available variables to check against

The following

global $hook_suffix, $typenow, $pagenow, $self, $parent_file, $submenu_file

are available on a wide range of admin pages. Use them to check if you're on the requested page that you need and only then do stuff.

// Example
if ( 'edit.php' !== $GLOBALS['pagenow'] )
    return;

Even better than testing against a variable, which can get reset on the fly (example) ...

$GLOBALS['wp'] = array( 'lost', 'my', 'contents', );

... is using the \WP_Screen object on admin pages:

add_action( 'admin_enqueue_scripts', function( $hook )
{
    /** @var \WP_Screen $screen */
    $screen = get_current_screen();

    var_dump( $screen );
    if ( 'post.php' !== $screen->base )
        return;
} );

Answer 2

function load_custom_wp_admin_style($hook) {
        // $hook is string value given add_menu_page function.
        if($hook != 'toplevel_page_mypluginname') {
                return;
        }
        wp_enqueue_style( 'custom_wp_admin_css', plugins_url('admin-style.css', __FILE__) );
}
add_action( 'admin_enqueue_scripts', 'load_custom_wp_admin_style' );