# PHP Attributes (Annotations)

Attributes (also known as annotations in other languages) offer a mechanism to add structured, machine-readable metadata declarations to your code. They were introduced in PHP 8.0.

Attributes can be applied to classes, methods, functions, parameters, properties, and class constants.

---

## 1. Syntax
Attributes are enclosed in hash-brackets `#[ ... ]`.

```php
#[Attribute]
class MyAttribute {
}

#[MyAttribute]
class MyClass {
}
```

## 2. Defining Custom Attributes
To create an attribute, you simply create a class and mark it with the `#[Attribute]` attribute itself.

```php
#[Attribute]
class Route {
    public $path;
    public $method;

    public function __construct($path, $method = 'GET') {
        $this->path = $path;
        $this->method = $method;
    }
}
```

## 3. Applying Attributes
You can pass arguments to the attribute constructor when applying it.

```php
#[Route('/home', method: 'GET')]
function home() {
    // ...
}
```

## 4. Reading Attributes (Reflection)
Attributes don't do anything by themselves. You use the **Reflection API** to read them at runtime.

```php
$reflection = new ReflectionFunction('home');
$attributes = $reflection->getAttributes(Route::class);

foreach ($attributes as $attribute) {
    $route = $attribute->newInstance();
    echo $route->path; // Outputs: /home
}
```

[[programming/php/php]] [[programming/php/php-reflection]]