Immutable
An immutable object, exhibiting immutability, is an object that can’t be changed. It may be created, read and cloned. On the other hand, a mutable object may change when one of its method is called, even if this is not visible from the outside.
Immutable objects are thread-safe.
Immutable objects often return a clone version of themselves, after modification.
<?php
class Elephpant {
private $age = 0;
function inc() : self {
$return = clone $this;
$return->age +=1;
return $return;
}
}
$elephpant = new elephpant();
$olderElephpant = $elephpant->inc();
// $elephpant and $olderElephpant are two distinct objects
?>
See Also
- The case for immutability
- Elegant immutable object pattern in PHP
- Immutable Objects in PHP: Your Secret Weapon for Safer Applications