PHP 手册
后退章 19. 类与对象（PHP 5）前进


Reflection

Introduction

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:

<?php
class Reflection { }
interface Reflector { }
class ReflectionException extends Exception { }
class ReflectionFunction implements Reflector { }
class ReflectionParameter implements Reflector { }
class ReflectionMethod extends ReflectionFunction { }
class ReflectionClass implements Reflector { }
class ReflectionObject extends ReflectionClass { }
class ReflectionProperty implements Reflector { }
class ReflectionExtension implements Reflector { }
?>

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

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

例子 19-31. Basic usage of the reflection API

<?php
Reflection::export(new ReflectionClass('Exception'));
?>

上例将输出：

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

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

ReflectionFunction

The ReflectionFunction class lets you reverse-engineer functions.

<?php
class ReflectionFunction implements Reflector
{
    final private __clone()
    public object __construct(string name)
    public string __toString()
    public static string export()
    public string getName()
    public bool isInternal()
    public bool isUserDefined()
    public string getFileName()
    public int getStartLine()
    public int getEndLine()
    public string getDocComment()
    public array getStaticVariables()
    public mixed invoke(mixed* args)
    public mixed invokeArgs(array args)
    public bool returnsReference()
    public ReflectionParameter[] getParameters()
    public int getNumberOfParameters()
    public int getNumberOfRequiredParameters()
}
?>

注: 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.

例子 19-32. Using the ReflectionFunction class

<?php
/**
* A simple counter
*
* @return    int
*/
function counter()
{
    static $c = 0;
    return $c++;
}

// Create an instance of the Reflection_Function class
$func = new ReflectionFunction('counter');

// Print out basic information
printf(
    "===> The %s function '%s'\n".
    "     declared in %s\n".
    "     lines %d to %d\n",
    $func->isInternal() ? 'internal' : 'user-defined',
    $func->getName(),
    $func->getFileName(),
    $func->getStartLine(),
    $func->getEndline()
);

// Print documentation comment
printf("---> Documentation:\n %s\n", var_export($func->getDocComment(), 1));

// Print static variables if existant
if ($statics = $func->getStaticVariables())
{
    printf("---> Static variables: %s\n", var_export($statics, 1));
}

// Invoke the function
printf("---> Invokation results in: ");
var_dump($func->invoke());


// you may prefer to use the export() method
echo "\nReflectionFunction::export() results:\n";
echo ReflectionFunction::export('counter');
?>

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

ReflectionParameter

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

<?php
class ReflectionParameter implements Reflector
{
    final private __clone()
    public object __construct(string name)
    public string __toString()
    public static string export()
    public string getName()
    public bool isPassedByReference()
    public ReflectionClass getClass()
    public bool isArray()
    public bool allowsNull()
    public bool isOptional()
    public bool isDefaultValueAvailable()
    public mixed getDefaultValue()
}
?>

注: getDefaultValue(), isDefaultValueAvailable() and isOptional() were added in PHP 5.0.3, while isArray() was added in PHP 5.1.0.

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.

例子 19-33. Using the ReflectionParameter class

<?php
function foo($a, $b, $c) { }
function bar(Exception $a, &$b, $c) { }
function baz(ReflectionFunction $a, $b = 1, $c = null) { }
function abc() { }

// Create an instance of Reflection_Function with the
// parameter given from the command line.    
$reflect = new ReflectionFunction($argv[1]);

echo $reflect;

foreach ($reflect->getParameters() as $i => $param) {
    printf(
        "-- Parameter #%d: %s {\n".
        "   Class: %s\n".
        "   Allows NULL: %s\n".
        "   Passed to by reference: %s\n".
        "   Is optional?: %s\n".
        "}\n",
        $i,
        $param->getName(),
        var_export($param->getClass(), 1),
        var_export($param->allowsNull(), 1),
        var_export($param->isPassedByReference(), 1),
        $param->isOptional() ? 'yes' : 'no'
    );
}
?>

ReflectionClass

The ReflectionClass class lets you reverse-engineer classes.

<?php
class ReflectionClass implements Reflector
{
    final private __clone()
    public object __construct(string name)
    public string __toString()
    public static string export()
    public string getName()
    public bool isInternal()
    public bool isUserDefined()
    public bool isInstantiable()
    public bool hasConstant(string name)
    public bool hasMethod(string name)
    public bool hasProperty(string name)
    public string getFileName()
    public int getStartLine()
    public int getEndLine()
    public string getDocComment()
    public ReflectionMethod getConstructor()
    public ReflectionMethod getMethod(string name)
    public ReflectionMethod[] getMethods()
    public ReflectionProperty getProperty(string name)
    public ReflectionProperty[] getProperties()
    public array getConstants()
    public mixed getConstant(string name)
    public ReflectionClass[] getInterfaces()
    public bool isInterface()
    public bool isAbstract()
    public bool isFinal()
    public int getModifiers()
    public bool isInstance(stdclass object)
    public stdclass newInstance(mixed* args)
    public ReflectionClass getParentClass()
    public bool isSubclassOf(ReflectionClass class)
    public array getStaticProperties()
    public mixed getStaticPropertyValue(string name [, mixed default])
    public void setStaticPropertyValue(string name, mixed value)
    public array getDefaultProperties()
    public bool isIterateable()
    public bool implementsInterface(string name)
    public ReflectionExtension getExtension()
    public string getExtensionName()
}
?>

注: hasConstant(), hasMethod(), hasProperty(), getStaticPropertyValue() and setStaticPropertyValue() were added in PHP 5.1.0.

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.

例子 19-34. Using the ReflectionClass class

<?php
interface Serializable
{
    // ...
}

class Object
{
    // ...
}

/**
* A counter class
*/
class Counter extends Object implements Serializable
{
    const START = 0;
    private static $c = Counter::START;

    /**
     * Invoke counter
     *
     * @access  public
     * @return  int
     */
    public function count() {
        return self::$c++;
    }
}

// Create an instance of the ReflectionClass class
$class = new ReflectionClass('Counter');

// Print out basic information
printf(
    "===> The %s%s%s %s '%s' [extends %s]\n" .
    "     declared in %s\n" .
    "     lines %d to %d\n" .
    "     having the modifiers %d [%s]\n",
        $class->isInternal() ? 'internal' : 'user-defined',
        $class->isAbstract() ? ' abstract' : '',
        $class->isFinal() ? ' final' : '',
        $class->isInterface() ? 'interface' : 'class',
        $class->getName(),
        var_export($class->getParentClass(), 1),
        $class->getFileName(),
        $class->getStartLine(),
        $class->getEndline(),
        $class->getModifiers(),
        implode(' ', Reflection::getModifierNames($class->getModifiers()))
);

// Print documentation comment
printf("---> Documentation:\n %s\n", var_export($class->getDocComment(), 1));

// Print which interfaces are implemented by this class
printf("---> Implements:\n %s\n", var_export($class->getInterfaces(), 1));

// Print class constants
printf("---> Constants: %s\n", var_export($class->getConstants(), 1));

// Print class properties
printf("---> Properties: %s\n", var_export($class->getProperties(), 1));

// Print class methods
printf("---> Methods: %s\n", var_export($class->getMethods(), 1));

// If this class is instantiable, create an instance
if ($class->isInstantiable()) {
    $counter = $class->newInstance();

    echo '---> $counter is instance? ';
    echo $class->isInstance($counter) ? 'yes' : 'no';

    echo "\n---> new Object() is instance? ";
    echo $class->isInstance(new Object()) ? 'yes' : 'no';
}
?>

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

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

ReflectionMethod

The ReflectionMethod class lets you reverse-engineer class methods.

<?php
class ReflectionMethod extends ReflectionFunction
{
    public __construct(mixed class, string name)
    public string __toString()
    public static string export()
    public mixed invoke(stdclass object, mixed* args)
    public mixed invokeArgs(stdclass object, array args)
    public bool isFinal()
    public bool isAbstract()
    public bool isPublic()
    public bool isPrivate()
    public bool isProtected()
    public bool isStatic()
    public bool isConstructor()
    public bool isDestructor()
    public int getModifiers()
    public ReflectionClass getDeclaringClass()

    // Inherited from ReflectionFunction
    final private __clone()
    public string getName()
    public bool isInternal()
    public bool isUserDefined()
    public string getFileName()
    public int getStartLine()
    public int getEndLine()
    public string getDocComment()
    public array getStaticVariables()
    public bool returnsReference()
    public ReflectionParameter[] getParameters()
    public int getNumberOfParameters()
    public int getNumberOfRequiredParameters()
}
?>

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.

例子 19-35. Using the ReflectionMethod class

<?php
class Counter
{
    private static $c = 0;

    /**
     * Increment counter
     *
     * @final
     * @static
     * @access  public
     * @return  int
     */
    final public static function increment()
    {
        return ++self::$c;
    }
}

// Create an instance of the Reflection_Method class
$method = new ReflectionMethod('Counter', 'increment');

// Print out basic information
printf(
    "===> The %s%s%s%s%s%s%s method '%s' (which is %s)\n" .
    "     declared in %s\n" .
    "     lines %d to %d\n" .
    "     having the modifiers %d[%s]\n",
        $method->isInternal() ? 'internal' : 'user-defined',
        $method->isAbstract() ? ' abstract' : '',
        $method->isFinal() ? ' final' : '',
        $method->isPublic() ? ' public' : '',
        $method->isPrivate() ? ' private' : '',
        $method->isProtected() ? ' protected' : '',
        $method->isStatic() ? ' static' : '',
        $method->getName(),
        $method->isConstructor() ? 'the constructor' : 'a regular method',
        $method->getFileName(),
        $method->getStartLine(),
        $method->getEndline(),
        $method->getModifiers(),
        implode(' ', Reflection::getModifierNames($method->getModifiers()))
);

// Print documentation comment
printf("---> Documentation:\n %s\n", var_export($method->getDocComment(), 1));

// Print static variables if existant
if ($statics= $method->getStaticVariables()) {
    printf("---> Static variables: %s\n", var_export($statics, 1));
}

// Invoke the method
printf("---> Invokation results in: ");
var_dump($method->invoke(NULL));
?>

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

注: 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.

ReflectionProperty

The ReflectionProperty class lets you reverse-engineer class properties.

<?php
class ReflectionProperty implements Reflector
{
    final private __clone()
    public __construct(mixed class, string name)
    public string __toString()
    public static string export()
    public string getName()
    public bool isPublic()
    public bool isPrivate()
    public bool isProtected()
    public bool isStatic()
    public bool isDefault()
    public int getModifiers()
    public mixed getValue(stdclass object)
    public void setValue(stdclass object, mixed value)
    public ReflectionClass getDeclaringClass()
    public string getDocComment()
}
?>

注: 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.

例子 19-36. Using the ReflectionProperty class

<?php
class String
{
    public $length  = 5;
}

// Create an instance of the ReflectionProperty class
$prop = new ReflectionProperty('String', 'length');

// Print out basic information
printf(
    "===> The%s%s%s%s property '%s' (which was %s)\n" .
    "     having the modifiers %s\n",
        $prop->isPublic() ? ' public' : '',
        $prop->isPrivate() ? ' private' : '',
        $prop->isProtected() ? ' protected' : '',
        $prop->isStatic() ? ' static' : '',
        $prop->getName(),
        $prop->isDefault() ? 'declared at compile-time' : 'created at run-time',
        var_export(Reflection::getModifierNames($prop->getModifiers()), 1)
);

// Create an instance of String
$obj= new String();

// Get current value
printf("---> Value is: ");
var_dump($prop->getValue($obj));

// Change value
$prop->setValue($obj, 10);
printf("---> Setting value to 10, new value is: ");
var_dump($prop->getValue($obj));

// Dump object
var_dump($obj);
?>

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

ReflectionExtension

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

<?php
class ReflectionExtension implements Reflector {
    final private __clone()
    public __construct(string name)
    public string __toString()
    public static string export()
    public string getName()
    public string getVersion()
    public ReflectionFunction[] getFunctions()
    public array getConstants()
    public array getINIEntries()
    public ReflectionClass[] getClasses()
    public array getClassNames()
}
?>

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.

例子 19-37. Using the ReflectionExtension class

<?php
// Create an instance of the ReflectionProperty class
$ext = new ReflectionExtension('standard');

// Print out basic information
printf(
    "Name        : %s\n" .
    "Version     : %s\n" .
    "Functions   : [%d] %s\n" .
    "Constants   : [%d] %s\n" .
    "INI entries : [%d] %s\n" .
    "Classes     : [%d] %s\n",
        $ext->getName(),
        $ext->getVersion() ? $ext->getVersion() : 'NO_VERSION',
        sizeof($ext->getFunctions()),
        var_export($ext->getFunctions(), 1),

        sizeof($ext->getConstants()),
        var_export($ext->getConstants(), 1),

        sizeof($ext->getINIEntries()),
        var_export($ext->getINIEntries(), 1),

        sizeof($ext->getClassNames()),
        var_export($ext->getClassNames(), 1)
);
?>

Extending the reflection classes

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.

例子 19-38. Extending the built-in classes

<?php
/**
* My Reflection_Method class
*/
class My_Reflection_Method extends ReflectionMethod
{
    public $visibility = '';

    public function __construct($o, $m)
    {
        parent::__construct($o, $m);
        $this->visibility= Reflection::getModifierNames($this->getModifiers());
    }
}

/**
* Demo class #1
*
*/
class T {
    protected function x() {}
}

/**
* Demo class #2
*
*/
class U extends T {
    function x() {}
}

// Print out information
var_dump(new My_Reflection_Method('U', 'x'));
?>

注: 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


add a note add a note User Contributed Notes
no dot prob at gmx dot net
02-Jun-2006 04:09
I have written a function which returns the value of a given DocComment tag.

Full example:

<?php

header('Content-Type: text/plain');

class Example
{
   /**
     * This is my DocComment!
     *
     * @DocTag: prints Hello World!
     */
   public function myMethod()
   {
       echo 'Hello World!';
   }
}

function getDocComment($str, $tag = '')
{
   if (empty($tag))
   {
       return $str;
   }

   $matches = array();
   preg_match("/".$tag.":(.*)(\\r\\n|\\r|\\n)/U", $str, $matches);

   if (isset($matches[1]))
   {
       return trim($matches[1]);
   }

   return '';
}

$method = new ReflectionMethod('Example', 'myMethod');

// will return Hello World!
echo getDocComment($method->getDocComment(), '@DocTag');

?>

Maybe you can add this functionality to the getDocComment methods of the reflection classes.
dave at dgx dot cz
26-Feb-2006 03:08
answer to [russ dot collier at gmail dot com]:

ReflectionClass::getProperties() method _DOES_ return inherited properties when reflecting subclasses. Only private properties of subclasses are hidden (of course). And ReflectionClass::getMethods() _DOES_ returns inherited methods.
CodeDuck at gmx dot net
09-Feb-2006 12:07
Beware, the Reflection reflects only the information right after compile time based on the definitions, not based on runtime objects. Might be obvious, wasn't for me, until the app throws the exception at my head.

Example:

<?php

class A {
   public $a = null;

   function set() {
     $this->foo = 'bar';
   }
}

$a = new A;
$a->set();

// works fine
$Reflection = new ReflectionProperty($a, 'a');

// throws exception
$Reflection = new ReflectionProperty($a, 'foo');

?>
salsi at icosaedro dot it
26-Nov-2005 04:14
I think all the "final private" methods should be made simply "private", or maybe they might be dropped at all from the declarations.

Some __construct() methods are reported to return something, but actually they should return "void".
walter dot huijbers at gmail dot com
28-Apr-2005 08:28
The wonderfull example code of russ collier works great until using it in combination with an interface or another abstract class, wich forces to define a function or variable in the loadable dynamic class, and the loaded class doesn't implement all the abstract functions. Ofcourse the class should not be used and an error should be reported, but the reported error is a Fatal error and is impossible to catch. This way it is impossible to, for example, generate an error message displaying the name of the file from wich the class is loaded.

Having dynamicly loadable classes with a forced interface can be very usefull when working on big projects or giving third parties the ability to provide new plugins. Considering this (imho) it would be nice to provide a clean error message to the writer of the plugin.

Please correct me if I'm wrong.
russ dot collier at gmail dot com
11-Dec-2004 11:34
While this is probably obvious to many people (it wasn't to me ;-P), the ReflectionClass::getProperties() method does _NOT_ return inherited properties when reflecting subclasses.
russ dot collier at gmail dot com
20-Oct-2004 11:40
Actually, aside from my inconsistent order of keywords in the 2 factory methods ;-) the Triangle::getInstance() method has 1 glaring flaw: it never actually sets the Triangle::$instance property. The correct way to implement a Singleton this way would be to replace Triangle::getInstance() with this:

<?php

   static public function getInstance()
   {

       if ( null == self::$instance )
       {

           self::$instance = new self;

           return self::$instance;

       }

       return self::$instance;

   }

?>
russ dot collier at gmail dot com
19-Oct-2004 12:40
If you've ever wanted to do dynamic class loading in PHP5, especially when the class you're trying to dynamically load is a Singleton (and therefore you cannot use the new operator), you can do something like this example below, using the PHP5 Reflection API:

<?php

abstract class Shape
{

   static public function makeShape( $shapeName )
   {

       $shapeInstance = null;

       $shapeClass = new ReflectionClass( $shapeName );

       $shapeMethod = $shapeClass->getMethod( 'getInstance' );

       $shapeInstance = $shapeMethod->invoke( null );

       $shapeClass  = null;
       $shapeMethod = null;

       return $shapeInstance;

   }

   abstract public function doStuff();

}

class Triangle extends Shape
{

   private static $instance = null;

   private function __construct() { }

   public static function getInstance()
   {

       if ( null == self::$instance )
       {

           self::$instance = new self;

       }

       return self::$instance;

   }

   public function doStuff() { }

}

$typeOfShape = 'Triangle';

$shape = null;

try
{

   $shape = Shape::makeShape( $typeOfShape );

}
catch ( Exception $e )
{

   print "Error creating shape '$typeOfShape'! " . $e->getMessage() . "\n";

}

if ( null != $shape )
{

   // $shape will be an instance of Triangle
   $shape->doStuff();

}

?>

So by changing the value of $typeOfShape you can dynamically load the appropriate Shape subclass at runtime, thus facilitating a sort of plug-in style architecture for your classes. You can just drop in new Shape subclasses and not have to modify any of the Shape class code to support them in its factory method makeShape() :-)

If your subclasses are all in separate files, you could even make the 'including' of these files dynamic as well, by adding these lines to the Shape::makeShape() method after the $shapeInstance is initialized:

<?php

ini_set( 'include_path', ini_get( 'include_path' ) . PATH_SEPARATOR .
         '/path/to/your/php/class/include/files' );

/**
 * Assuming your subclasses are in files called 'class_$shapeName.php' :-)
 * Of course doing a dynamic require() could be a security problem depending
 * on how you validate/clean your $shapeName method parameter (if at all ;-))
 */
require_once( "class_$shapeName.php" );

?>
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