PHP Type Safety

Combine runtime assertions (webmozarts/assert) with static analysis annotations (PHPDoc shapes, templates) to write PHP code that is safe at runtime and satisfies PHPStan/Psalm at strict levels. The two approaches are complementary: PHPDoc narrows types for the analyser, assertions enforce them at runtime where PHP's type system cannot.

Setup

composer require webmozart/assert
composer require --dev phpstan/phpstan-webmozart-assert  # PHPStan users only

The PHPStan extension translates Assert::*() calls into type-narrowing expressions so PHPStan refines variable types after each assertion. If you use phpstan/extension-installer it registers automatically; otherwise add it to phpstan.neon: