我知道PHP还没有本地枚举。但是我已经习惯了来自Java世界的它们。我喜欢使用枚举来提供ide的自动补全功能能够理解的预定义值。

常量可以解决这个问题,但是存在名称空间冲突问题,而且(实际上是因为)它们是全局的。数组没有名称空间的问题,但是它们太模糊了,它们可以在运行时被覆盖,而且ide很少知道如何在没有额外的静态分析注释或属性的情况下自动填充它们的键。

你有什么常用的解决方案/变通办法吗?有人记得PHP的人对枚举有什么想法或决定吗?


当前回答

我在github上找到了这个库,我认为它提供了一个非常不错的答案。

PHP枚举实现灵感来自脾

你可以输入:function setAction(Action $ Action) { 你可以用方法丰富枚举(例如format, parse,…) 您可以扩展枚举以添加新值(将枚举设置为final以防止出现这种情况) 您可以得到所有可能值的列表(见下面)

宣言

<?php
use MyCLabs\Enum\Enum;

/**
 * Action enum
 */
class Action extends Enum
{
    const VIEW = 'view';
    const EDIT = 'edit';
}

使用

<?php
$action = new Action(Action::VIEW);

// or
$action = Action::VIEW();

类型提示枚举值:

<?php
function setAction(Action $action) {
    // ...
}

其他回答

我已经在这里评论了一些其他的答案,所以我想我也会发表意见。 最后,由于PHP不支持类型化枚举,您可以选择以下两种方式之一:删除类型化枚举,或者接受它们极难有效删除的事实。

我更倾向于接受事实,而不是使用其他答案以某种方式使用的const方法:

abstract class Enum
{

    const NONE = null;

    final private function __construct()
    {
        throw new NotSupportedException(); // 
    }

    final private function __clone()
    {
        throw new NotSupportedException();
    }

    final public static function toArray()
    {
        return (new ReflectionClass(static::class))->getConstants();
    }

    final public static function isValid($value)
    {
        return in_array($value, static::toArray());
    }

}

枚举示例:

final class ResponseStatusCode extends Enum
{

    const OK                         = 200;
    const CREATED                    = 201;
    const ACCEPTED                   = 202;
    // ...
    const SERVICE_UNAVAILABLE        = 503;
    const GATEWAY_TIME_OUT           = 504;
    const HTTP_VERSION_NOT_SUPPORTED = 505;

}

使用Enum作为所有其他枚举扩展的基类,允许使用诸如toArray、isValid等辅助方法。对我来说,类型化的枚举(以及管理它们的实例)最终太混乱了。


假设

如果存在一个__getStatic魔法方法(最好还有一个__equals魔法方法),那么大部分问题都可以通过一种多吨模式来缓解。

(以下是假设;它不会起作用,尽管也许有一天它会)

final class TestEnum
{

    private static $_values = [
        'FOO' => 1,
        'BAR' => 2,
        'QUX' => 3,
    ];
    private static $_instances = [];

    public static function __getStatic($name)
    {
        if (isset(static::$_values[$name]))
        {
            if (empty(static::$_instances[$name]))
            {
                static::$_instances[$name] = new static($name);
            }
            return static::$_instances[$name];
        }
        throw new Exception(sprintf('Invalid enumeration value, "%s"', $name));
    }

    private $_value;

    public function __construct($name)
    {
        $this->_value = static::$_values[$name];
    }

    public function __equals($object)
    {
        if ($object instanceof static)
        {
            return $object->_value === $this->_value;
        }
        return $object === $this->_value;
    }

}

$foo = TestEnum::$FOO; // object(TestEnum)#1 (1) {
                       //   ["_value":"TestEnum":private]=>
                       //   int(1)
                       // }

$zap = TestEnum::$ZAP; // Uncaught exception 'Exception' with message
                       // 'Invalid enumeration member, "ZAP"'

$qux = TestEnum::$QUX;
TestEnum::$QUX == $qux; // true
'hello world!' == $qux; // false

还有一个本地扩展。的SplEnum

脾提供了模拟和创建枚举对象的能力 原生的PHP。

http://www.php.net/manual/en/class.splenum.php

注意:

https://www.php.net/manual/en/spl-types.installation.php

PECL扩展没有与PHP绑定。 此PECL扩展的DLL目前不可用。

基于此要点,所有枚举的基类:

abstract class Enum {
    protected $val;

    protected function __construct($arg) {
        $this->val = $arg;
    }

    public function __toString() {
        return $this->val;
    }

    public function __set($arg1, $arg2) {
        throw new Exception("enum does not have property");
    }

    public function __get($arg1) {
        throw new Exception("enum does not have property");
    }

    // not really needed
    public function __call($arg1, $arg2) {
        throw new Exception("enum does not have method");
    }

    // not really needed
    static public function __callStatic($arg1, $arg2) {
        throw new Exception("enum does not have static method");
    }
}

你的枚举:

final class MyEnum extends Enum {
    static public function val1() {
        return new self("val1");
    }

    static public function val2() {
        return new self("val2");
    }

    static public function val3() {
        return new self("val3");
    }
}

测试:

$a = MyEnum::val1();
echo "1.the enum value is '$a'\n";

function consumeMyEnum(MyEnum $arg) {
    return "2.the return value is '$arg'\n";
}

echo consumeMyEnum($a);
$version = explode(".", PHP_VERSION);
if ($version[0] >= 7) {
    try {
        echo consumeMyEnum("val1");
    } catch (TypeError $e) {
        echo "3.passing argument error happens (PHP 7.0 and above)\n";
    }
}

echo ($a == MyEnum::val1()) ? "4.same\n" : "4.different\n";
echo ($a == MyEnum::val2()) ? "5.same\n" : "5.different\n";

$b = MyEnum::val1();
echo ($a == $b)  ? "6.same\n" : "6.different\n";
echo ($a === $b) ? "7.same\n" : "7.different\n";

$c = MyEnum::val2();
echo ($a == $c)  ? "8.same\n" : "8.different\n";
echo ($a === $c) ? "9.same\n" : "9.different\n";

switch ($c) {
    case MyEnum::val1(): echo "10.case of 1st\n"; break;
    case MyEnum::val2(): echo "11.case of 2nd\n"; break;
    case MyEnum::val3(): echo "12.case of 3rd\n"; break;
}

try {
    $a->prop = 10;
} catch (Exception $e) {
    echo "13.set property error happens\n";
}

try {
    echo $a->prop;
} catch (Exception $e) {
    echo "14.get property error happens\n";
}

try {
    echo $a->meth();
} catch (Exception $e) {
    echo "15.method call error happens\n";
}

try {
    echo MyEnum::meth();
} catch (Exception $e) {
    echo "16.static method call error happens\n";
}

class Ordinary {}
echo $a instanceof MyEnum   ? "17.MyEnum instance\n"   : "17.not MyEnum instance\n";
echo $a instanceof Enum     ? "18.Enum instance\n"     : "18.not Enum instance\n";
echo $a instanceof Ordinary ? "19.Ordinary instance\n" : "19.not Ordinary instance\n";

在网上试试:沙盒

昨天我在博客上写了这门课。我认为在php脚本中使用它可能很容易:

final class EnumException extends Exception{}

abstract class Enum
{
    /**
     * @var array ReflectionClass
     */
    protected static $reflectorInstances = array();
    /**
     * Массив конфигурированного объекта-константы enum
     * @var array
     */
    protected static $enumInstances = array();
    /**
     * Массив соответствий значение->ключ используется для проверки - 
     * если ли константа с таким значением
     * @var array
     */
    protected static $foundNameValueLink = array();

    protected $constName;
    protected $constValue;

    /**
     * Реализует паттерн "Одиночка"
     * Возвращает объект константы, но но как объект его использовать не стоит, 
     * т.к. для него реализован "волшебный метод" __toString()
     * Это должно использоваться только для типизачии его как параметра
     * @paradm Node
     */
    final public static function get($value)
    {
        // Это остается здесь для увеличения производительности (по замерам ~10%)
        $name = self::getName($value);
        if ($name === false)
            throw new EnumException("Неизвестая константа");
        $className = get_called_class();    
        if (!isset(self::$enumInstances[$className][$name]))
        {
            $value = constant($className.'::'.$name);
            self::$enumInstances[$className][$name] = new $className($name, $value);
        }

        return self::$enumInstances[$className][$name];
    }

    /**
     * Возвращает массив констант пар ключ-значение всего перечисления
     * @return array 
     */
    final public static function toArray()
    {
        $classConstantsArray = self::getReflectorInstance()->getConstants();
        foreach ($classConstantsArray as $k => $v)
            $classConstantsArray[$k] = (string)$v;
        return $classConstantsArray;
    }

    /**
     * Для последующего использования в toArray для получения массива констант ключ->значение 
     * @return ReflectionClass
     */
    final private static function getReflectorInstance()
    {
        $className = get_called_class();
        if (!isset(self::$reflectorInstances[$className]))
        {
            self::$reflectorInstances[$className] = new ReflectionClass($className);
        }
        return self::$reflectorInstances[$className];
    }

    /**
     * Получает имя константы по её значению
     * @param string $value
     */
    final public static function getName($value)
    {
        $className = (string)get_called_class();

        $value = (string)$value;
        if (!isset(self::$foundNameValueLink[$className][$value]))
        {
            $constantName = array_search($value, self::toArray(), true);
            self::$foundNameValueLink[$className][$value] = $constantName;
        }
        return self::$foundNameValueLink[$className][$value];
    }

    /**
     * Используется ли такое имя константы в перечислении
     * @param string $name
     */
    final public static function isExistName($name)
    {
        $constArray = self::toArray();
        return isset($constArray[$name]);
    }

    /**
     * Используется ли такое значение константы в перечислении
     * @param string $value
     */
    final public static function isExistValue($value)
    {
        return self::getName($value) === false ? false : true;
    }   


    final private function __clone(){}

    final private function __construct($name, $value)
    {
        $this->constName = $name;
        $this->constValue = $value;
    }

    final public function __toString()
    {
        return (string)$this->constValue;
    }
}

用法:

class enumWorkType extends Enum
{
        const FULL = 0;
        const SHORT = 1;
}

我使用带有常量的类:

class Enum {
    const NAME       = 'aaaa';
    const SOME_VALUE = 'bbbb';
}

print Enum::NAME;