PHP: 匿名类_Manual_20160511

匿名类

PHP 7 开始支持匿名类。匿名类很有用，可以创建一次性的简单对象。

<?php

// PHP 7 之前的代码
class Logger
{
    public function log($msg)
    {
        echo $msg;
    }
}

$util->setLogger(new Logger());

// 使用了 PHP 7+ 后的代码
$util->setLogger(new class {
    public function log($msg)
    {
        echo $msg;
    }
});

可以传递参数到匿名类的构造器，也可以扩展（extend）其他类、实现接口（implement interface），以及像其他普通的类一样使用 trait：

<?php

class SomeClass {}
interface SomeInterface {}
trait SomeTrait {}

var_dump(new class(10) extends SomeClass implements SomeInterface {
    private $num;

    public function __construct($num)
    {
        $this->num = $num;
    }

    use SomeTrait;
});

以上例程会输出：

object(class@anonymous)#1 (1) { ["Command line code0x104c5b612":"class@anonymous":private]=> int(10)
}

匿名类被嵌套进普通 Class 后，不能访问这个外部类（Outer class）的 private（私有）、protected（受保护）方法或者属性。为了访问外部类（Outer class）protected 属性或方法，匿名类可以 extend（扩展）此外部类。为了使用外部类（Outer class）的 private 属性，必须通过构造器传进来：

<?php

class Outer
{
    private $prop = 1;
    protected $prop2 = 2;

    protected function func1()
    {
        return 3;
    }

    public function func2()
    {
        return new class($this->prop) extends Outer {
            private $prop3;

            public function __construct($prop)
            {
                $this->prop3 = $prop;
            }

            public function func3()
            {
                return $this->prop2 + $this->prop3 + $this->func1();
            }
        };
    }
}

echo (new Outer)->func2()->func3();

以上例程会输出：

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User Contributed Notes 3 notes

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Anonymous ¶

1 month ago

Below three examples describe anonymous class with very simple and basic but quite understandable example

<?php
// First way - anonymous class assigned directly to variable
$ano_class_obj = new class{
    public $prop1 = 'hello';
    public $prop2 = 754;
    const SETT = 'some config';

    public function getValue()
    {
        // do some operation
        return 'some returned value';
    }

    public function getValueWithArgu($str)
    {
        // do some operation
        return 'returned value is '.$str;
    }
};

echo "\n";

var_dump($ano_class_obj);
echo "\n";

echo $ano_class_obj->prop1;
echo "\n";

echo $ano_class_obj->prop2;
echo "\n";

echo $ano_class_obj::SETT;
echo "\n";

echo $ano_class_obj->getValue();
echo "\n";

echo $ano_class_obj->getValueWithArgu('OOP');
echo "\n";

echo "\n";

// Second way - anonymous class assigned to variable via defined function
$ano_class_obj_with_func = ano_func();

function ano_func()
{
    return new class {
        public $prop1 = 'hello';
        public $prop2 = 754;
        const SETT = 'some config';

        public function getValue()
        {
            // do some operation
            return 'some returned value';
        }

        public function getValueWithArgu($str)
        {
            // do some operation
            return 'returned value is '.$str;
        }
    };
}

echo "\n";

var_dump($ano_class_obj_with_func);
echo "\n";

echo $ano_class_obj_with_func->prop1;
echo "\n";

echo $ano_class_obj_with_func->prop2;
echo "\n";

echo $ano_class_obj_with_func::SETT;
echo "\n";

echo $ano_class_obj_with_func->getValue();
echo "\n";

echo $ano_class_obj_with_func->getValueWithArgu('OOP');
echo "\n";

echo "\n";

// Third way - passing argument to anonymous class via constructors
$arg = 1; // we got it by some operation
$config = [2, false]; // we got it by some operation
$ano_class_obj_with_arg = ano_func_with_arg($arg, $config);

function ano_func_with_arg($arg, $config)
{
    return new class($arg, $config) {
        public $prop1 = 'hello';
        public $prop2 = 754;
        public $prop3, $config;
        const SETT = 'some config';

        public function __construct($arg, $config)
        {
            $this->prop3 = $arg;
            $this->config =$config;
        }

        public function getValue()
        {
            // do some operation
            return 'some returned value';
        }

        public function getValueWithArgu($str)
        {
            // do some operation
            return 'returned value is '.$str;
        }
    };
}

echo "\n";

var_dump($ano_class_obj_with_arg);
echo "\n";

echo $ano_class_obj_with_arg->prop1;
echo "\n";

echo $ano_class_obj_with_arg->prop2;
echo "\n";

echo $ano_class_obj_with_arg::SETT;
echo "\n";

echo $ano_class_obj_with_arg->getValue();
echo "\n";

echo $ano_class_obj_with_arg->getValueWithArgu('OOP');
echo "\n";

echo "\n";

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Theriault ¶

1 month ago

Despite being anonymous, anonymous classes are named. get_declared_classes() will return anonymous classes (PHP 7.0.5).

Because they are named, an anonymous class can also be aliased (not that its useful):
<?php
$a = new class { public $test = 123; };
class_alias(get_class($a), "Test");
$b = new Test;
echo $b->test; // outputs 123
?>

Unlike anonymous functions, returning an anonymous class from a function will be a new instance of the SAME anonymous class each time.

<?php
function anonymous_function () {
   return function () {
      static $shared = 0;
      echo ++$shared;
   };
};
function anonymous_class() {
   return new class {
      static $shared = 0;
      public function __construct() {
         echo ++self::$shared;
      }
   };
}

anonymous_function(); // outputs 1
anonymous_function(); // outputs 1

anonymous_class(); // outputs 1
anonymous_class(); // outputs 2

get_class(anonymous_class()) === get_class(anonymous_class()); // TRUE
?>

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-2

sam dot wankaner at gmail dot com ¶

1 month ago

Below two examples describe anonymous class with very simple and basic but quite understandable example

<?php
// anonymous_class.php
// PHP 7

// First way - anonymous class assigned directly to variable
$ano_class_obj = new class{
    public $prop1 = 'hello';
    public $prop2 = 754;
    const SETT = 'some config';

    public function getValue()
    {
        // do some operation
        return 'some returned value';
    }

    public function getValueWithArgu($str)
    {
        // do some operation
        return 'returned value is '.$str;
    }
};

echo "\n";

var_dump($ano_class_obj);
echo "\n";

echo $ano_class_obj->prop1;
echo "\n";

echo $ano_class_obj->prop2;
echo "\n";

echo $ano_class_obj::SETT;
echo "\n";

echo $ano_class_obj->getValue();
echo "\n";

echo $ano_class_obj->getValueWithArgu('OOP');
echo "\n";

echo "\n";

// Second way - anonymous class assigned to variable via defined function
$ano_class_obj_with_func = ano_func();

function ano_func()
{
    return new class {
        public $prop1 = 'hello';
        public $prop2 = 754;
        const SETT = 'some config';

        public function getValue()
        {
            // do some operation
            return 'some returned value';
        }

        public function getValueWithArgu($str)
        {
            // do some operation
            return 'returned value is '.$str;
        }
    };
}

echo "\n";

var_dump($ano_class_obj_with_func);
echo "\n";

echo $ano_class_obj_with_func->prop1;
echo "\n";

echo $ano_class_obj_with_func->prop2;
echo "\n";

echo $ano_class_obj_with_func::SETT;
echo "\n";

echo $ano_class_obj_with_func->getValue();
echo "\n";

echo $ano_class_obj_with_func->getValueWithArgu('OOP');
echo "\n";

echo "\n";

// Third way - passing argument to anonymous class via constructors
$arg = 1; // we got it by some operation
$config = [2, false]; // we got it by some operation
$ano_class_obj_with_arg = ano_func_with_arg($arg, $config);

function ano_func_with_arg($arg, $config)
{
    return new class($arg, $config) {
        public $prop1 = 'hello';
        public $prop2 = 754;
        public $prop3, $config;
        const SETT = 'some config';

        public function __construct($arg, $config)
        {
            $this->prop3 = $arg;
            $this->config =$config;
        }

        public function getValue()
        {
            // do some operation
            return 'some returned value';
        }

        public function getValueWithArgu($str)
        {
            // do some operation
            return 'returned value is '.$str;
        }
    };
}

echo "\n";

var_dump($ano_class_obj_with_arg);
echo "\n";

echo $ano_class_obj_with_arg->prop1;
echo "\n";

echo $ano_class_obj_with_arg->prop2;
echo "\n";

echo $ano_class_obj_with_arg::SETT;
echo "\n";

echo $ano_class_obj_with_arg->getValue();
echo "\n";

echo $ano_class_obj_with_arg->getValueWithArgu('OOP');
echo "\n";

echo "\n";

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