Form submit fails

Hello
I created this code snippet, according to forum help, and activated it:

add_action( 'template_redirect', function () { 

	if ( ! is_page( 82154 ) || ! isset( $_POST['name'] ) ) {
		return;
	}

	$name = $_POST['name'];
	// process submitted data here
	echo $name;

} );

Then a page with ID 82154 with a form:

 
<form action="" method="POST">
<label>Nome</label>
<input name="name" required="" type="text" />

<label>Cognome</label>
<input name="surname" required="" type="text" />

<label>A quale evento vuoi iscriverti?</label>

<select name="event" required="">
<option hidden="" selected="selected" value="">-</option>
<option value="uno">Lorem</option>
<option value="due">Ipsum</option>
<option value="tre">Dolor</option>
<option value="quattro">Sit</option>
<option value="cinque">Amen</option>
<option value="sei">Latinum</option>
</select>

<label>eMail</label>
<input name="email" required="" type="text" />

<input type="submit" value="Submit" />

</form>&nbsp;

When I test the page, I get a “Oops! Something went wrong…”
I think I followed the indication, but I cannot understand what is wrong.

Thanks for help!
Alberto