peachpie-docs/docs/net/attributes.md

It is possible to annotate class or interface declaration or a function declaration with both - CLR attributes and PHP attributes. Use the PHP 8 syntax to specify the attribute type name, its parameters and properties.

PHP attributes

Attributes can be applied to classes, interfaces, traits, functions, properties, and class constants.

Attribute syntax

<?php

#[System\ObsoleteAttribute("An attribute parameter")] // attribute annotation refering to a .NET attribute
class X {

    #[Amazon\Lambda\Core\LambdaSerializerAttribute(Amazon\Lambda\Serialization\Json\JsonSerializer::class)]
    function foo() {
        // ...
    }
}

The sample above depicts the use of .NET attributes on a PHP type and PHP function. The attribute is enclosed in #[ and ] symbols. Follows the type name according to PHP syntax and optional round parenthesis with the attribute parameters.

Following syntaxes are possible:

#[AttributeTypeName]
#[AttributeTypeName()]
#[AttributeTypeName(Value)]
#[AttributeTypeName(Value1, Value2)]
#[AttributeTypeName(Parameter1 = Value1, Parameter2 = Value2)]

The Value can be a number, string, TypeName::class specifying a System\Type, a class constant, an enumeration member, a global constant, or a simple expression that is resolvable in compile time.

Pchp.Core.PhpCustomAttribute

In case the specified attribute does not get resolved as a valid .NET System.Attribute type, the compiler treats it as an instance of Pchp.Core.PhpCustomAttrubite that encapsulates the attribute information. This is used for further PHP reflection using ReflectionAttribite class.

<?php

#[Something]
class X {
}

The sample above gets compiled to following CIL metadata:

[Pchp.Core.PhpCustomAttribute("Something", new byte[0])]
public class X

@deprecated PHPDoc tag

Classes and functions annotated with @deprecated PHPDoc tag are implicitly annotated with .NET System.ObsoleteAttribute.

<?php

/**
 * @deprecated This class is old.
 */
class X {
}

This is useful for the interoperability with .NET languages, i.e. the C# diagnostics will provide information about the use of deprecated types and methods.