我使用接口而不是类:

interface DaysOfWeek
{
    const Sunday = 0;
    const Monday = 1;
    // etc.
}

var $today = DaysOfWeek::Sunday;

这里有一些很好的解决方案!

这是我的版本。

它是强类型的 它与IDE自动补全一起工作 枚举由代码和描述定义，其中代码可以是整数、二进制值、短字符串或基本上任何您想要的内容。可以很容易地扩展该模式以支持其他属性。 它支持值(==)和引用(===)比较，并在switch语句中工作。

我认为主要的缺点是枚举成员必须分别声明和实例化，这是由于描述和PHP不能在静态成员声明时构造对象。我想绕过这个问题的一种方法可能是使用带有解析过的文档注释的反射。

抽象枚举看起来像这样:

<?php

abstract class AbstractEnum
{
    /** @var array cache of all enum instances by class name and integer value */
    private static $allEnumMembers = array();

    /** @var mixed */
    private $code;

    /** @var string */
    private $description;

    /**
     * Return an enum instance of the concrete type on which this static method is called, assuming an instance
     * exists for the passed in value.  Otherwise an exception is thrown.
     *
     * @param $code
     * @return AbstractEnum
     * @throws Exception
     */
    public static function getByCode($code)
    {
        $concreteMembers = &self::getConcreteMembers();

        if (array_key_exists($code, $concreteMembers)) {
            return $concreteMembers[$code];
        }

        throw new Exception("Value '$code' does not exist for enum '".get_called_class()."'");
    }

    public static function getAllMembers()
    {
        return self::getConcreteMembers();
    }

    /**
     * Create, cache and return an instance of the concrete enum type for the supplied primitive value.
     *
     * @param mixed $code code to uniquely identify this enum
     * @param string $description
     * @throws Exception
     * @return AbstractEnum
     */
    protected static function enum($code, $description)
    {
        $concreteMembers = &self::getConcreteMembers();

        if (array_key_exists($code, $concreteMembers)) {
            throw new Exception("Value '$code' has already been added to enum '".get_called_class()."'");
        }

        $concreteMembers[$code] = $concreteEnumInstance = new static($code, $description);

        return $concreteEnumInstance;
    }

    /**
     * @return AbstractEnum[]
     */
    private static function &getConcreteMembers() {
        $thisClassName = get_called_class();

        if (!array_key_exists($thisClassName, self::$allEnumMembers)) {
            $concreteMembers = array();
            self::$allEnumMembers[$thisClassName] = $concreteMembers;
        }

        return self::$allEnumMembers[$thisClassName];
    }

    private function __construct($code, $description)
    {
        $this->code = $code;
        $this->description = $description;
    }

    public function getCode()
    {
        return $this->code;
    }

    public function getDescription()
    {
        return $this->description;
    }
}

下面是一个具体枚举示例:

<?php

require('AbstractEnum.php');

class EMyEnum extends AbstractEnum
{
    /** @var EMyEnum */
    public static $MY_FIRST_VALUE;
    /** @var EMyEnum */
    public static $MY_SECOND_VALUE;
    /** @var EMyEnum */
    public static $MY_THIRD_VALUE;

    public static function _init()
    {
        self::$MY_FIRST_VALUE = self::enum(1, 'My first value');
        self::$MY_SECOND_VALUE = self::enum(2, 'My second value');
        self::$MY_THIRD_VALUE = self::enum(3, 'My third value');
    }
}

EMyEnum::_init();

可以这样使用:

<?php

require('EMyEnum.php');

echo EMyEnum::$MY_FIRST_VALUE->getCode().' : '.EMyEnum::$MY_FIRST_VALUE->getDescription().PHP_EOL.PHP_EOL;

var_dump(EMyEnum::getAllMembers());

echo PHP_EOL.EMyEnum::getByCode(2)->getDescription().PHP_EOL;

并产生如下输出:

1 : My first value array(3) { [1]=> object(EMyEnum)#1 (2) { ["code":"AbstractEnum":private]=> int(1) ["description":"AbstractEnum":private]=> string(14) "My first value" } [2]=> object(EMyEnum)#2 (2) { ["code":"AbstractEnum":private]=> int(2) ["description":"AbstractEnum":private]=> string(15) "My second value" } [3]=> object(EMyEnum)#3 (2) { ["code":"AbstractEnum":private]=> int(3) ["description":"AbstractEnum":private]=> string(14) "My third value" } } My second value

一个不使用反射的更简单、更轻的版本:

abstract class enum {
    private function __construct() {}
    static function has($const) {
        $name = get_called_class();
        return defined("$name::$const");
    }
    static function value($const) {
        $name = get_called_class();
        return defined("$name::$const")? constant("$name::$const") : false;
    }
}

用法:

class requestFormat  extends enum { const HTML = 1; const JSON = 2; const XML  = 3; const FORM = 4; }

echo requestFormat::value('JSON'); // 2
echo requestFormat::has('JSON');   // true

这提供了常量的优势，也允许检查它们的有效性，但它缺乏更复杂的解决方案所提供的其他花哨功能，更明显的是无法检查值的反向(在上面的例子中，你不能检查'2'是否是一个有效值)

我使用接口而不是类:

interface DaysOfWeek
{
    const Sunday = 0;
    const Monday = 1;
    // etc.
}

var $today = DaysOfWeek::Sunday;

如果您需要使用全局唯一的enum(即即使在不同enum之间比较元素时)并且易于使用，请随意使用以下代码。我还添加了一些我认为有用的方法。您可以在代码顶部的注释中找到示例。

<?php

/**
 * Class Enum
 * 
 * @author Christopher Fox <christopher.fox@gmx.de>
 *
 * @version 1.0
 *
 * This class provides the function of an enumeration.
 * The values of Enum elements are unique (even between different Enums)
 * as you would expect them to be.
 *
 * Constructing a new Enum:
 * ========================
 *
 * In the following example we construct an enum called "UserState"
 * with the elements "inactive", "active", "banned" and "deleted".
 * 
 * <code>
 * Enum::Create('UserState', 'inactive', 'active', 'banned', 'deleted');
 * </code>
 *
 * Using Enums:
 * ============
 *
 * The following example demonstrates how to compare two Enum elements
 *
 * <code>
 * var_dump(UserState::inactive == UserState::banned); // result: false
 * var_dump(UserState::active == UserState::active); // result: true
 * </code>
 *
 * Special Enum methods:
 * =====================
 *
 * Get the number of elements in an Enum:
 *
 * <code>
 * echo UserState::CountEntries(); // result: 4
 * </code>
 *
 * Get a list with all elements of the Enum:
 *
 * <code>
 * $allUserStates = UserState::GetEntries();
 * </code>
 *
 * Get a name of an element:
 *
 * <code>
 * echo UserState::GetName(UserState::deleted); // result: deleted
 * </code>
 *
 * Get an integer ID for an element (e.g. to store as a value in a database table):
 * This is simply the index of the element (beginning with 1).
 * Note that this ID is only unique for this Enum but now between different Enums.
 *
 * <code>
 * echo UserState::GetDatabaseID(UserState::active); // result: 2
 * </code>
 */
class Enum
{

    /**
     * @var Enum $instance The only instance of Enum (Singleton)
     */
    private static $instance;

    /**
     * @var array $enums    An array of all enums with Enum names as keys
     *          and arrays of element names as values
     */
    private $enums;

    /**
     * Constructs (the only) Enum instance
     */
    private function __construct()
    {
        $this->enums = array();
    }

    /**
     * Constructs a new enum
     *
     * @param string $name The class name for the enum
     * @param mixed $_ A list of strings to use as names for enum entries
     */
    public static function Create($name, $_)
    {
        // Create (the only) Enum instance if this hasn't happened yet
        if (self::$instance===null)
        {
            self::$instance = new Enum();
        }

        // Fetch the arguments of the function
        $args = func_get_args();
        // Exclude the "name" argument from the array of function arguments,
        // so only the enum element names remain in the array
        array_shift($args);
        self::$instance->add($name, $args);
    }

    /**
     * Creates an enumeration if this hasn't happened yet
     * 
     * @param string $name The class name for the enum
     * @param array $fields The names of the enum elements
     */
    private function add($name, $fields)
    {
        if (!array_key_exists($name, $this->enums))
        {
            $this->enums[$name] = array();

            // Generate the code of the class for this enumeration
            $classDeclaration =     "class " . $name . " {\n"
                        . "private static \$name = '" . $name . "';\n"
                        . $this->getClassConstants($name, $fields)
                        . $this->getFunctionGetEntries($name)
                        . $this->getFunctionCountEntries($name)
                        . $this->getFunctionGetDatabaseID()
                        . $this->getFunctionGetName()
                        . "}";

            // Create the class for this enumeration
            eval($classDeclaration);
        }
    }

    /**
     * Returns the code of the class constants
     * for an enumeration. These are the representations
     * of the elements.
     * 
     * @param string $name The class name for the enum
     * @param array $fields The names of the enum elements
     *
     * @return string The code of the class constants
     */
    private function getClassConstants($name, $fields)
    {
        $constants = '';

        foreach ($fields as $field)
        {
            // Create a unique ID for the Enum element
            // This ID is unique because class and variables
            // names can't contain a semicolon. Therefore we
            // can use the semicolon as a separator here.
            $uniqueID = $name . ";" . $field;
            $constants .=   "const " . $field . " = '". $uniqueID . "';\n";
            // Store the unique ID
            array_push($this->enums[$name], $uniqueID);
        }

        return $constants;
    }

    /**
     * Returns the code of the function "GetEntries()"
     * for an enumeration
     * 
     * @param string $name The class name for the enum
     *
     * @return string The code of the function "GetEntries()"
     */
    private function getFunctionGetEntries($name) 
    {
        $entryList = '';        

        // Put the unique element IDs in single quotes and
        // separate them with commas
        foreach ($this->enums[$name] as $key => $entry)
        {
            if ($key > 0) $entryList .= ',';
            $entryList .= "'" . $entry . "'";
        }

        return  "public static function GetEntries() { \n"
            . " return array(" . $entryList . ");\n"
            . "}\n";
    }

    /**
     * Returns the code of the function "CountEntries()"
     * for an enumeration
     * 
     * @param string $name The class name for the enum
     *
     * @return string The code of the function "CountEntries()"
     */
    private function getFunctionCountEntries($name) 
    {
        // This function will simply return a constant number (e.g. return 5;)
        return  "public static function CountEntries() { \n"
            . " return " . count($this->enums[$name]) . ";\n"
            . "}\n";
    }

    /**
     * Returns the code of the function "GetDatabaseID()"
     * for an enumeration
     * 
     * @return string The code of the function "GetDatabaseID()"
     */
    private function getFunctionGetDatabaseID()
    {
        // Check for the index of this element inside of the array
        // of elements and add +1
        return  "public static function GetDatabaseID(\$entry) { \n"
            . "\$key = array_search(\$entry, self::GetEntries());\n"
            . " return \$key + 1;\n"
            . "}\n";
    }

    /**
     * Returns the code of the function "GetName()"
     * for an enumeration
     *
     * @return string The code of the function "GetName()"
     */
    private function getFunctionGetName()
    {
        // Remove the class name from the unique ID 
        // and return this value (which is the element name)
        return  "public static function GetName(\$entry) { \n"
            . "return substr(\$entry, strlen(self::\$name) + 1 , strlen(\$entry));\n"
            . "}\n";
    }

}


?>

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