universal-header.php

<?php


defined('ABSPATH') or die('What are you looking for?');


/** Handle the HTML */
function my_custom_header_branda_shortcode_function( ){

    ob_start(); ?>


	<div id="my-custom-header">
		<?php
			wp_nav_menu( [
				'theme_location' => 'custom_universal_header'
			]);
		?>
	</div>


	<?php return ob_get_clean();

}

/** Styles **/
function custom_header_style_branda_header_function(){

	?>

	<style>
		#my-custom-header ul{
			display: flex;
			justify-content: space-between;
			list-style: none;
		}
	</style>

  <?php

}

/** Scripts */
function custom_header_scripts_branda_header_function(){

	?>

	<script>
		alert('function enabled');
	</script>

  <?php

}

/*** Let's make a custom menu */
function custom_branda_menu_register(){
	register_nav_menus(
		[
		'custom_universal_header' => __( 'Universal Header', 'my-textdomain' ),
		]
	);
}

/** Hooks */

add_shortcode( 'branda-custom-header','my_custom_header_branda_shortcode_function', 0 );
add_action( 'wp_head','custom_header_style_branda_header_function', 10 );
//add_action( 'wp_footer','custom_header_scripts_branda_header_function', 999 );
add_action( 'after_setup_theme','custom_branda_menu_register', 10 );