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";
    }

}


?>

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;
}

我知道这是一个非常非常非常古老的话题，但我对此有一个想法，想知道人们是怎么想的。

注:我在玩这个，并意识到如果我只是修改__call()函数，你可以更接近实际的枚举。__call()函数处理所有未知函数调用。假设你想创建三个枚举RED_LIGHT, YELLOW_LIGHT和GREEN_LIGHT。你现在只需做以下事情就可以做到:

$c->RED_LIGHT();
$c->YELLOW_LIGHT();
$c->GREEN_LIGHT();

一旦定义了，你所要做的就是再次调用它们来获取值:

echo $c->RED_LIGHT();
echo $c->YELLOW_LIGHT();
echo $c->GREEN_LIGHT();

得到0 1 2。玩得开心!这个现在也在GitHub上。

更新:我已经这样做了，所以__get()和__set()函数现在都被使用。这允许您不必调用函数，除非您愿意。相反，现在你可以说:

$c->RED_LIGHT;
$c->YELLOW_LIGHT;
$c->GREEN_LIGHT;

对于价值的创造和获取。因为变量最初还没有定义，所以调用__get()函数(因为没有指定值)，它会发现数组中的条目还没有创建。因此，它创建条目，将最后一个给定值赋给它+1(+1)，对最后一个值变量加1，并返回TRUE。如果你设置这个值:

$c->RED_LIGHT = 85;

然后调用__set()函数，最后一个值被设置为新值+1(+1)。现在我们有了一个很好的方法来处理枚举，并且可以动态地创建它们。

<?php
################################################################################
#   Class ENUMS
#
#       Original code by Mark Manning.
#       Copyrighted (c) 2015 by Mark Manning.
#       All rights reserved.
#
#       This set of code is hereby placed into the free software universe
#       via the GNU greater license thus placing it under the Copyleft
#       rules and regulations with the following modifications:
#
#       1. You may use this work in any other work.  Commercial or otherwise.
#       2. You may make as much money as you can with it.
#       3. You owe me nothing except to give me a small blurb somewhere in
#           your program or maybe have pity on me and donate a dollar to
#           sim_sales@paypal.com.  :-)
#
#   Blurb:
#
#       PHP Class Enums by Mark Manning (markem-AT-sim1-DOT-us).
#       Used with permission.
#
#   Notes:
#
#       VIM formatting.  Set tabs to four(4) spaces.
#
################################################################################
class enums
{
    private $enums;
    private $clear_flag;
    private $last_value;

################################################################################
#   __construct(). Construction function.  Optionally pass in your enums.
################################################################################
function __construct()
{
    $this->enums = array();
    $this->clear_flag = false;
    $this->last_value = 0;

    if( func_num_args() > 0 ){
        return $this->put( func_get_args() );
        }

    return true;
}
################################################################################
#   put(). Insert one or more enums.
################################################################################
function put()
{
    $args = func_get_args();
#
#   Did they send us an array of enums?
#   Ex: $c->put( array( "a"=>0, "b"=>1,...) );
#   OR  $c->put( array( "a", "b", "c",... ) );
#
    if( is_array($args[0]) ){
#
#   Add them all in
#
        foreach( $args[0] as $k=>$v ){
#
#   Don't let them change it once it is set.
#   Remove the IF statement if you want to be able to modify the enums.
#
            if( !isset($this->enums[$k]) ){
#
#   If they sent an array of enums like this: "a","b","c",... then we have to
#   change that to be "A"=>#. Where "#" is the current count of the enums.
#
                if( is_numeric($k) ){
                    $this->enums[$v] = $this->last_value++;
                    }
#
#   Else - they sent "a"=>"A", "b"=>"B", "c"=>"C"...
#
                    else {
                        $this->last_value = $v + 1;
                        $this->enums[$k] = $v;
                        }
                }
            }
        }
#
#   Nope!  Did they just sent us one enum?
#
        else {
#
#   Is this just a default declaration?
#   Ex: $c->put( "a" );
#
            if( count($args) < 2 ){
#
#   Again - remove the IF statement if you want to be able to change the enums.
#
                if( !isset($this->enums[$args[0]]) ){
                    $this->enums[$args[0]] = $this->last_value++;
                    }
#
#   No - they sent us a regular enum
#   Ex: $c->put( "a", "This is the first enum" );
#
                    else {
#
#   Again - remove the IF statement if you want to be able to change the enums.
#
                        if( !isset($this->enums[$args[0]]) ){
                            $this->last_value = $args[1] + 1;
                            $this->enums[$args[0]] = $args[1];
                            }
                        }
                }
            }

    return true;
}
################################################################################
#   get(). Get one or more enums.
################################################################################
function get()
{
    $num = func_num_args();
    $args = func_get_args();
#
#   Is this an array of enums request? (ie: $c->get(array("a","b","c"...)) )
#
    if( is_array($args[0]) ){
        $ary = array();
        foreach( $args[0] as $k=>$v ){
            $ary[$v] = $this->enums[$v];
            }

        return $ary;
        }
#
#   Is it just ONE enum they want? (ie: $c->get("a") )
#
        else if( ($num > 0) && ($num < 2) ){
            return $this->enums[$args[0]];
            }
#
#   Is it a list of enums they want? (ie: $c->get( "a", "b", "c"...) )
#
        else if( $num > 1 ){
            $ary = array();
            foreach( $args as $k=>$v ){
                $ary[$v] = $this->enums[$v];
                }

            return $ary;
            }
#
#   They either sent something funky or nothing at all.
#
    return false;
}
################################################################################
#   clear(). Clear out the enum array.
#       Optional.  Set the flag in the __construct function.
#       After all, ENUMS are supposed to be constant.
################################################################################
function clear()
{
    if( $clear_flag ){
        unset( $this->enums );
        $this->enums = array();
        }

    return true;
}
################################################################################
#   __call().  In case someone tries to blow up the class.
################################################################################
function __call( $name, $arguments )
{
    if( isset($this->enums[$name]) ){ return $this->enums[$name]; }
        else if( !isset($this->enums[$name]) && (count($arguments) > 0) ){
            $this->last_value = $arguments[0] + 1;
            $this->enums[$name] = $arguments[0];
            return true;
            }
        else if( !isset($this->enums[$name]) && (count($arguments) < 1) ){
            $this->enums[$name] = $this->last_value++;
            return true;
            }

    return false;
}
################################################################################
#   __get(). Gets the value.
################################################################################
function __get($name)
{
    if( isset($this->enums[$name]) ){ return $this->enums[$name]; }
        else if( !isset($this->enums[$name]) ){
            $this->enums[$name] = $this->last_value++;
            return true;
            }

    return false;
}
################################################################################
#   __set().  Sets the value.
################################################################################
function __set( $name, $value=null )
{
    if( isset($this->enums[$name]) ){ return false; }
        else if( !isset($this->enums[$name]) && !is_null($value) ){
            $this->last_value = $value + 1;
            $this->enums[$name] = $value;
            return true;
            }
        else if( !isset($this->enums[$name]) && is_null($value) ){
            $this->enums[$name] = $this->last_value++;
            return true;
            }

    return false;
}
################################################################################
#   __destruct().  Deconstruct the class.  Remove the list of enums.
################################################################################
function __destruct()
{
    unset( $this->enums );
    $this->enums = null;

    return true;
}

}
#
#   Test code
#
#   $c = new enums();
#   $c->RED_LIGHT(85);
#   $c->YELLOW_LIGHT = 23;
#   $c->GREEN_LIGHT;
#
#   echo $c->RED_LIGHT . "\n";
#   echo $c->YELLOW_LIGHT . "\n";
#   echo $c->GREEN_LIGHT . "\n";

?>

类常量呢?

<?php

class YourClass
{
    const SOME_CONSTANT = 1;

    public function echoConstant()
    {
        echo self::SOME_CONSTANT;
    }
}

echo YourClass::SOME_CONSTANT;

$c = new YourClass;
$c->echoConstant();

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

公认的答案是要走的路，实际上这是我所做的简单。枚举提供了大多数优点(可读、快速等)。然而，这里缺少一个概念:类型安全。在大多数语言中，枚举也用于限制允许的值。下面是一个通过使用私有构造函数、静态实例化方法和类型检查来获得类型安全的例子:

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

 private $intVal;
 private function __construct($intVal){
   $this->intVal = $intVal;
 }

 //static instantiation methods
 public static function MONDAY(){
   return new self(self::Monday);
 }
 //etc.
}

//function using type checking
function printDayOfWeek(DaysOfWeek $d){ //compiler can now use type checking
  // to something with $d...
}

//calling the function is safe!
printDayOfWeek(DaysOfWeek::MONDAY());

我们甚至可以更进一步:在DaysOfWeek类中使用常量可能会导致误用:例如，人们可能会这样错误地使用它:

printDayOfWeek(DaysOfWeek::Monday); //triggers a compiler error.

这是错误的(调用整数常量)。我们可以使用私有静态变量而不是常量来防止这种情况:

class DaysOfWeeks{

  private static $monday = 1;
  //etc.

  private $intVal;
  //private constructor
  private function __construct($intVal){
    $this->intVal = $intVal;
  }

  //public instantiation methods
  public static function MONDAY(){
    return new self(self::$monday);
  }
  //etc.


  //convert an instance to its integer value
  public function intVal(){
    return $this->intVal;
  }

}

当然，不可能访问整数常量(这实际上是目的)。intVal方法允许将DaysOfWeek对象转换为其整数表示形式。

请注意，我们甚至可以进一步在实例化方法中实现缓存机制，以在广泛使用枚举的情况下节省内存…

希望这能有所帮助