shortcode php wordpress

1
<?php echo do_shortcode("[your_shortcode]"); ?>

<?php echo do_shortcode('[name_of_shortcode]'); ?>

// function that runs when shortcode is called
function wpb_demo_shortcode() { 
 
// Things that you want to do. 
$message = 'Hello world!'; 
 
// Output needs to be return
return $message;
} 
// register shortcode
add_shortcode('greeting', 'wpb_demo_shortcode'); 

function user() {     
 ob_start();
 include(get_stylesheet_directory() . '/tutorial.php');
 return ob_get_clean();
}
add_shortcode( 'countdown', 'user' );