Create a admin main wordpress custom menu item

PHP

public function create_menu_item() {
		/**
		 * Register a custom menu page.
		 */
		function wpdocs_register_my_custom_menu_page() {
		    add_menu_page(
		        __( 'Custom Menu Title', 'textdomain' ),
		        'custom menu',
		        'manage_options',
		        'myplugin/myplugin-admin.php',
		        '',
		        plugins_url( 'myplugin/images/icon.png' ),
		        6
		    );
		}
		add_action( 'admin_menu', 'wpdocs_register_my_custom_menu_page' );
	}