PHP Cast to my class

Question

why this is not possible:

$user = (User) $u[0]; 

but this is possible

$bool = (boolean) $res['success']; 

I use PHP 7.0.

Answer 1

As I know, in PHP you can only cast to some types:

(int), (integer) - cast to integer (bool), (boolean) - cast to boolean (float), (double), (real) - cast to float (string) - cast to string (binary) - cast to binary string (PHP 6) (array) - cast to array (object) - cast to object (unset) - cast to NULL (PHP 5) (depracted in PHP 7.2) (removed in 8.0) 

(see Type Casting)

Instead you could use instanceof to check of specific type:

if($yourvar instanceof YourClass) {     //DO something } else {     throw new Exception('Var is not of type YourClass'); } 

EDIT

As mentioned by Szabolcs Páll in his answer, it is also possible to declare a return type or parameter type, but in that cases an exception (TypeError) will be throwen, if the type does not match.

function test(): string {     return 'test'; }  function test(string $test){     return "test" . $test; } 

Since PHP 7.2 it is also possible to make the types nullable by adding ? in front of them:

function test(): ?string {     return null; }