do_head_items example

global $concatenate_scripts;

    if ( ! did_action( 'wp_print_scripts' ) ) {
        /** This action is documented in wp-includes/functions.wp-scripts.php */
        do_action( 'wp_print_scripts' );
    }

    $wp_scripts = wp_scripts();

    script_concat_settings();
    $wp_scripts->do_concat = $concatenate_scripts;
    $wp_scripts->do_head_items();

    /** * Filters whether to print the head scripts. * * @since 2.8.0 * * @param bool $print Whether to print the head scripts. Default true. */
    if ( apply_filters( 'print_head_scripts', true ) ) {
        _print_scripts();
    }