Typed Collection is an attempt to use the concept of “Generics” from other programming languages in PHP as well. Unfortunately, not all advantages can be realized with current PHP on-board means and syntax.
class A {}
class B extends A {}
// Creata a collection which can only contain instances of A.
// Sub classes of A and other classes *are not allowed*:
$collection = new \Serens\TypedCollection\ClassCollection(A::class);
$collection[] = new \A(); // ok
$collection[] = new \B(); // will fail (InvalidArgumentException)
// Creata a collection which can only contain instances of \Iterable.
// Sub classes *are allowed*:
$collection = new \Serens\TypedCollection\InstanceCollection(\Iterator::class);
$collection[] = new \EmptyIterator(); // ok
// Create a collection which can only contain strings:
$collection = new \Serens\TypedCollection\ScalarCollection(\Serens\TypedCollection\ScalarType::STRING);
$collection[] = 'A string can be added to this collection.'; // ok
$collection[] = 324; // will fail (InvalidArgumentException)
// The constructor also accepts initialization values:
$collection = new \Serens\TypedCollection\ScalarCollection(
\Serens\TypedCollection\ScalarType::STRING,
[ 'A string', 'Another string', 'The last string' ]
);Both collections work very similarly. The difference is that the
ClassCollection can only hold instances of a specific, exact class. The
InstanceCollection, on the other hand, can also include instances of
derived classes of the specified parent class. The InstanceCollection is
more suitable for interfaces.
A major disadvantage is that static code analysis or even the type hinting of the IDE know nothing about the configured types of a collection. Elements of type 'mixed' are always recognized for them.
If you absolutely want to use type hinting, you can derive a typed collection and overwrite all relevant methods and determine the type using PHPDoc. However, this approach would generate a lot of code that would mainly consist of parent calls and PHPDocs.