Phpstan

Name: PHPStan Description: Static analysis tool configured at Level 9. All code must pass PHPStan Level 9 with strict typing, no untyped signatures, and minimal suppression of errors. Compatible Agents: general-purpose, testing, backend Tags: app//*.php, tests//*.php, laravel, php, static-analysis, phpstan, types

Rules

• All code must pass PHPStan Level 9
• Type hints on all parameters, return types, and properties — no untyped signatures
• No @phpstan-ignore unless documented with a justification comment
• Use phpstan-assert, phpstan-param, and phpstan-return PHPDoc tags when generics or complex types are needed
• Replace mixed with specific union types where possible
• Use array<string, mixed> instead of bare array in PHPDoc
• Add @throws annotations for methods that throw exceptions
• Use assert() or type narrowing instead of suppressing errors

Examples

// ✓ Specific types instead of mixed
public function process(Order $order): Invoice { ... }

// ✓ PHPDoc with typed arrays
/**
 * @return array<string, array<int, string|object>>
 */
public function rules(): array { ... }

// ✓ Union types instead of mixed
public function format(string|int|null $value): string { ... }

// ✓ Generics for collections
/**
 * @return Collection<int, Invoice>
 */
public function getInvoices(): Collection { ... }

// ✓ @throws annotation
/**
 * @throws InvoiceAlreadyPaidException
 */
public function markAsPaid(Invoice $invoice): void
{
    if ($invoice->isPaid()) {
        throw InvoiceAlreadyPaidException::for($invoice);
    }
    // ...
}

// ✓ Type narrowing with assert() instead of suppression
public function handle(mixed $model): void
{
    assert($model instanceof Invoice);
    $model->markAsPaid(); // PHPStan now knows it's an Invoice
}

// ✓ Justified suppression with comment
/** @phpstan-ignore-next-line Property accessed via magic method — documented in IDE helper */
$user->custom_attribute;

Anti-Patterns

• Using bare mixed types when a more specific type is possible
• Using bare array without a PHPDoc generic shape: array<string, mixed>
• Using @phpstan-ignore without a comment explaining why it is necessary
• Omitting @throws annotations on methods that throw
• Leaving parameters, return types, or properties untyped
• Using (int), (string) casts as substitutes for proper type narrowing

References

• PHPStan Documentation
• PHPStan Rule Levels
• Related: PHP/SKILL.md — general PHP conventions including strict typing