Array Shape Property gets overwritten by Subclasses #15330

Overriden properties with different types are not sound because they are both readable and writable by parent and child classes. So the parent class wouldn't know it has to assign the extra offsets the child class wants there.

This error can be turned off by setting reportMaybesInPropertyPhpDocTypes: false.

Personally I wouldn't choose to do inheritance here at all, but rather composition with interfaces. Options are implementation detail of a single implementation. If you're trying to store a file and you want different backends, you can pass options to the different backend classes through constructor, they do not need to have a common parent class, only a common interface you will typehint in the rest of the system.

Stub files are per class, so each of the three classes can have its own shape. What makes the shapes clash is that Mage_Cache_Backend_File replaces the whole defaults array and leaves out hashed_directory_perm, cache_file_perm and metadatas_array_max_size. If Zend_Cache_Backend_File declares those keys as required, a Mage instance really breaks that promise (any Zend method reading them gets a missing key), so PHPStan reports the override as not covariant, and reportMaybesInPropertyPhpDocTypes: false does not turn that one off.

Declaring those three keys as optional in both shapes makes it work:

• Zend_Cache_Backend (stub): array<string, int|bool|string|null>
• Zend_Cache_Backend_File (stub): its keys, with hashed_directory_perm?: int, cache_file_perm?: int, metadatas_array_max_size?: int, plus ...<string, int|bool|string|null>
• Mage_Cache_Backend_File (its own docblock): its keys, the same three as optional, plus ...<string, int|bool|string|null>

Level 10 with bleeding edge, no errors, and $this->_options['file_name_prefix'] is string inside the Mage class: https://phpstan.org/r/8c73037f-4e20-470f-85b2-135ef596c20b

With phpstan-strict-rules on (as in your snippet), the two overrides are also reported as "not the same as" the parent type, because a writable property is only sound when its type is unchanged: https://phpstan.org/r/434c356a-0cb2-4274-806a-86443198ca86. That is the error that reportMaybesInPropertyPhpDocTypes: false turns off. With it, the same code passes.

The playground has no stub files, so the snippet declares the Zend classes inline. In a project, put those two class declarations, with only the $_options property and its @var, in a .stub file listed under stubFiles. I checked both setups locally on PHPStan 2.3.1.