Create custom post type

function.php

add_action( 'init', 'true_register_post_type_init' ); 
 
function true_register_post_type_init() {
	$labels = [
		'name' => 'Functions',
		'singular_name' => 'Function', // admin panel Add-> Function
		'add_new' => 'Add function',
		'add_new_item' => 'Add New function', // <title> tag title
		'edit_item' => 'Edit function',
		'new_item' => 'New feature',
		'all_items' => 'All functions',
		'view_item' => 'View function on site',
		'search_items' => 'Search functions',
		'not_found' =>  'No functions found.',
		'not_found_in_trash' => 'There are no functions in the basket.',
		'menu_name' => 'WP Code' // link in the admin menu
	];
	$args = [
		'labels' => $labels,
		'public' => true,
		'show_ui' => true, // show interface in admin panel
		'has_archive' => true, 
		'menu_icon' => get_stylesheet_directory_uri() .'/img/function_icon.png', // menu icon
		'menu_position' => 20, // order in the menu
		'supports' => array( 'title', 'editor', 'comments', 'author', 'thumbnail')
	];
	register_post_type('functions', $args);
}