SKILL.md
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Feature Availability by Version
Feature
Version
Rule Prefix
Union types, match, nullsafe, named args, constructor promotion, attributes
8.0+
type-, modern-
Enums, readonly properties, intersection types, first-class callables, never, fibers
8.1+
modern-
Readonly classes, DNF types, true/false/null standalone types
8.2+
modern-
Typed class constants, #[\Override], json_validate()
8.3+
modern-
Property hooks, asymmetric visibility, #[\Deprecated], new without parens
8.4+
modern-
Pipe operator
>
8.5+
Only suggest features available in the detected version. If the user asks about upgrading or newer features, mention what becomes available at each version.
When to Apply
Reference these guidelines when:
- Writing or reviewing PHP code
- Implementing classes and interfaces
- Using PHP 8.x modern features
- Ensuring type safety
- Following PSR standards
- Applying design patterns
Rule Categories by Priority
Priority
Category
Impact
Prefix
Rules
1
Type System
CRITICAL
type-
9
2
Modern PHP Features
CRITICAL
modern-
16
3
PSR Standards
HIGH
psr-
6
4
SOLID Principles
HIGH
solid-
5
5
Error Handling
HIGH
error-
5
6
Performance
MEDIUM
perf-
5
7
Security
CRITICAL
sec-
5
Quick Reference
1. Type System (CRITICAL) — 9 rules
type-strict-mode- Declare strict types in every file
type-return-types- Always declare return types
type-parameter-types- Type all parameters
type-property-types- Type class properties
type-union-types- Use union types effectively
type-intersection-types- Use intersection types
type-nullable-types- Handle nullable types properly
type-void-never- Use void/never for appropriate return types
type-mixed-avoid- Avoid mixed type when possible
2. Modern PHP Features (CRITICAL) — 16 rules
8.0+:
modern-constructor-promotion- Constructor property promotion
modern-match-expression- Match over switch
modern-named-arguments- Named arguments for clarity
modern-nullsafe-operator- Nullsafe operator (?->)
modern-attributes- Attributes for metadata
8.1+:
modern-enums- Enums instead of constants
modern-enums-methods- Enums with methods and interfaces
modern-readonly-properties- Readonly for immutable data
modern-first-class-callables- First-class callable syntax
modern-arrow-functions- Arrow functions (7.4+, pairs well with 8.1 features)
8.2+:
modern-readonly-classes- Readonly classes
8.3+:
modern-typed-constants- Typed class constants (const string NAME = 'foo')
modern-override-attribute-#[\Override]to catch parent method typos
8.4+:
modern-property-hooks- Property hooks replacing getters/setters
modern-asymmetric-visibility-public private(set)for controlled access
8.5+:
modern-pipe-operator- Pipe operator (|>) for functional chaining
3. PSR Standards (HIGH) — 6 rules
psr-4-autoloading- Follow PSR-4 autoloading
psr-12-coding-style- Follow PSR-12 coding style
psr-naming-classes- Class naming conventions
psr-naming-methods- Method naming conventions
psr-file-structure- One class per file
psr-namespace-usage- Proper namespace usage
4. SOLID Principles (HIGH) — 5 rules
solid-srp- Single Responsibility: one reason to change
solid-ocp- Open/Closed: extend, don't modify
solid-lsp- Liskov Substitution: subtypes must be substitutable
solid-isp- Interface Segregation: small, focused interfaces
solid-dip- Dependency Inversion: depend on abstractions
5. Error Handling (HIGH) — 5 rules
error-custom-exceptions- Create specific exceptions for different errors
error-exception-hierarchy- Organize exceptions into meaningful hierarchy
error-try-catch-specific- Catch specific exceptions, not generic \Exception
error-finally-cleanup- Use finally for guaranteed resource cleanup
error-never-suppress- Never use @ error suppression operator
6. Performance (MEDIUM) — 5 rules
perf-avoid-globals- Avoid global variables, use dependency injection
perf-lazy-loading- Defer expensive operations until needed
perf-array-functions- Use native array functions over manual loops
perf-string-functions- Use native string functions over regex
perf-generators- Use generators for large datasets
7. Security (CRITICAL) — 5 rules
sec-input-validation- Validate and sanitize all external input
sec-output-escaping- Escape output based on context (HTML, JS, URL)
sec-password-hashing- Use password_hash/verify, never MD5/SHA1
sec-sql-prepared- Use prepared statements for all SQL queries
sec-file-uploads- Validate file type, size, name; store outside web root
Essential Guidelines
For detailed examples and explanations, see the rule files:
- type-strict-mode.md - Strict types declaration
- modern-constructor-promotion.md - Constructor property promotion
- modern-enums.md - PHP 8.1+ enums with methods
- solid-srp.md - Single responsibility principle
Key Patterns (Quick Reference)
<?php
declare(strict_types=1);
// 8.0+ Constructor promotion + readonly (8.1+)
class User
{
public function __construct(
public readonly string $id,
private string $email,
) {}
}
// 8.1+ Enums with methods
enum Status: string
{
case Active = 'active';
case Inactive = 'inactive';
public function label(): string
{
return match($this) {
self::Active => 'Active',
self::Inactive => 'Inactive',
};
}
}
// 8.0+ Match expression
$result = match($status) {
'pending' => 'Waiting',
'active' => 'Running',
default => 'Unknown',
};
// 8.0+ Nullsafe operator
$country = $user?->getAddress()?->getCountry();
// 8.3+ Typed class constants + #[\Override]
class PaymentService extends BaseService
{
public const string GATEWAY = 'stripe';
#[\Override]
public function process(): void { /* ... */ }
}
// 8.4+ Property hooks + asymmetric visibility
class Product
{
public string $name { set => trim($value); }
public private(set) float $price;
}
// 8.5+ Pipe operator
$result = $input
|> trim(...)
|> strtolower(...)
|> htmlspecialchars(...);Output Format
When auditing code, output findings in this format:
file:line - [category] Description of issueExample:
src/Services/UserService.php:15 - [type] Missing return type declaration
src/Models/Order.php:42 - [modern] Use match expression instead of switch
src/Controllers/ApiController.php:28 - [solid] Class has multiple responsibilitiesHow to Use
Read individual rule files for detailed explanations:
rules/modern-constructor-promotion.md
rules/type-strict-mode.md
rules/solid-srp.md