Strictly speaking
$foo = ” is an empty (String)
$foo = null is nothing , not a number not a object , just nothing

In most ,if not all, programming languages null is not equal to an empty string or integer who’s value is zero.

PHP on the other appears to allow this

consider this example

function getPhoneNumberFromDatabase(){

if( $db->getConnection() == false ){
return null;
}

return $db->getPhoneNumber();
}

in many cases you will want your functions to return NULL upon failure

so if we do this

$phone = getPhoneNumberFromDatabase();
if( $phone == null ){
echo ‘Database connection failed’;
}

In this case , PHP will report that “Database connection failed” even if the connection is okay but the phone number was an empty string.

That’s why you should use is_null or === null

so, $foo = ” doesn’t make $foo null!
right?