Reflection

PHP 5 comes with a complete reflection API that adds the ability to reverse-engineer classes, interfaces, functions and methods as well as extensions. Additionally, the reflection API also offers ways of retrieving doc comments for functions, classes and methods.

The reflection API is an object-oriented extension to the Zend Engine, consisting of the following classes:

Poznámka: For details on these classes, have a look at the next chapters.

If we were to execute the code in the example below:

Class [ <internal> class Exception ] {

  - Constants [0] {
  }

  - Static properties [0] {
  }

  - Static methods [0] {
  }

  - Properties [6] {
    Property [ <default> protected $message ]
    Property [ <default> private $string ]
    Property [ <default> protected $code ]
    Property [ <default> protected $file ]
    Property [ <default> protected $line ]
    Property [ <default> private $trace ]
  }

  - Methods [9] {
    Method [ <internal> final private method __clone ] {
    }

    Method [ <internal> <ctor> public method __construct ] {

      - Parameters [2] {
        Parameter #0 [ <required> $message ]
        Parameter #1 [ <required> $code ]
      }
    }

    Method [ <internal> final public method getMessage ] {
    }

    Method [ <internal> final public method getCode ] {
    }

    Method [ <internal> final public method getFile ] {
    }

    Method [ <internal> final public method getLine ] {
    }

    Method [ <internal> final public method getTrace ] {
    }

    Method [ <internal> final public method getTraceAsString ] {
    }

    Method [ <internal> public method __toString ] {
    }
  }
}

     

ReflectionException extends the standard Exception and is thrown by Reflection API. No specific methods or properties are introduced.

The ReflectionFunction class lets you reverse-engineer functions.

Poznámka: getNumberOfParameters() and getNumberOfRequiredParameters() were added in PHP 5.0.3, while invokeArgs() was added in PHP 5.1.0.

To introspect a function, you will first have to create an instance of the ReflectionFunction class. You can then call any of the above methods on this instance.

Poznámka: The method invoke() accepts a variable number of arguments which are passed to the function just as in call_user_func().

The ReflectionParameter class retrieves information about a function's or method's parameters.

Poznámka: getDefaultValue(), isDefaultValueAvailable() and isOptional() were added in PHP 5.0.3, while isArray() was added in PHP 5.1.0. getDeclaringFunction() and getPosition() were added in PHP 5.1.3.

To introspect function parameters, you will first have to create an instance of the ReflectionFunction or ReflectionMethod classes and then use their getParameters() method to retrieve an array of parameters.

The ReflectionClass class lets you reverse-engineer classes.

Poznámka: hasConstant(), hasMethod(), hasProperty(), getStaticPropertyValue() and setStaticPropertyValue() were added in PHP 5.1.0, while newInstanceArgs() was added in PHP 5.1.3.

To introspect a class, you will first have to create an instance of the ReflectionClass class. You can then call any of the above methods on this instance.

Poznámka: The method newInstance() accepts a variable number of arguments which are passed to the function just as in call_user_func().

Poznámka: $class = new ReflectionClass('Foo'); $class->isInstance($arg) is equivalent to $arg instanceof Foo or is_a($arg, 'Foo').

The ReflectionObject class lets you reverse-engineer objects.

The ReflectionMethod class lets you reverse-engineer class methods.

To introspect a method, you will first have to create an instance of the ReflectionMethod class. You can then call any of the above methods on this instance.

Poznámka: Trying to invoke private, protected or abstract methods will result in an exception being thrown from the invoke() method.

Poznámka: For static methods as seen above, you should pass NULL as the first argument to invoke(). For non-static methods, pass an instance of the class.

The ReflectionProperty class lets you reverse-engineer class properties.

Poznámka: getDocComment() was added in PHP 5.1.0.

To introspect a property, you will first have to create an instance of the ReflectionProperty class. You can then call any of the above methods on this instance.

Poznámka: Trying to get or set private or protected class property's values will result in an exception being thrown.

The ReflectionExtension class lets you reverse-engineer extensions. You can retrieve all loaded extensions at runtime using the get_loaded_extensions().

To introspect an extension, you will first have to create an instance of the ReflectionExtension class. You can then call any of the above methods on this instance.

In case you want to create specialized versions of the built-in classes (say, for creating colorized HTML when being exported, having easy-access member variables instead of methods or having utility methods), you may go ahead and extend them.

Poznámka: Caution: If you're overwriting the constructor, remember to call the parent's constructor _before_ any code you insert. Failing to do so will result in the following: Fatal error: Internal error: Failed to retrieve the reflection object