difference between Null and False - php

Question

i watching tutorial about developing guestbook with php
this is the code that get the message with the id
public function GetMessage($id)
{
//Database
$id = (int)$id;
$gb_host = 'localhost' ;
$gb_dbname = 'guestbook' ;
$gb_username = 'root';
$gb_password = '' ;
$connection = mysqli_connect($gb_host , $gb_username , $gb_password,$gb_dbname);
$querycheck = mysqli_query($connection,"SELECT * FROM `messages` WHERE `id` = $id");
if($querycheck)
{
$message = mysqli_fetch_assoc($querycheck);
return $message;
}
else
{
mysqli_close($connection);
return NULL;
}
mysqli_close($connection);
}
why in else statment we return NULL instead of False
what's the difference between Null and False ?

Answer 1

The type.
False is boolean and null is a value.
So :
$test = false;
if($test === false) {
//correct
}
$test = null;
if ($test === false) {
//incorrect
} else if ($test === null) {
//correct
}
$test = false;
if(!$test) {
//correct
}
$test = null;
if(!$test) {
//correct
}
More precision in the documentation

Answer 2

Imho in this case and null and false are incorrect, because method should return one type of data!
In our method it should be array not special type (null) or boolean,
and it will be easy to use this method elsewhere, because everytime we know that we works with array, and we don't have write something like this:
$messages = $dao->GetMessage(27);
if (is_array($messages)) {
// ...
}
if (is_null($messages)) {
$messages = []; // because wihout it foreach will down
}
foreach ($messages as $message) {
// ...
}
And as for me it's pretty straightforward:
if we have data at db we'll receive not empty array,
if we don't have data at db - we'll receive empty array.
It's obviously!