本文实例讲述了PHP中Enum(枚举)用法。分享给大家供大家参考，具体如下：

PHP其实有Enum类库的，需要安装perl扩展，所以不是php的标准扩展，因此代码的实现需要运行的php环境支持。

(1)扩展类库SplEnum类。该类的摘要如下：

SplEnum extends SplType {

/* Constants */

const NULL __default = null ;

/* 方法 */

public array getConstList ([ bool $include_default = false ] )

/* 继承的方法 */

SplType::__construct ([ mixed $initial_value [, bool $strict ]] )

}

使用示例：

class Month extends SplEnum {

const __default = self::January;

const January = 1;

const February = 2;

const March = 3;

const April = 4;

const May = 5;

const June = 6;

const July = 7;

const August = 8;

const September = 9;

const October = 10;

const November = 11;

const December = 12;

}

echo new Month(Month::June) . PHP_EOL;

try {

new Month(13);

} catch (UnexpectedValueException $uve) {

echo $uve->getMessage() . PHP_EOL;

}

?>

输出结果：

6

Value not a const in enum Month

(2)自定义的Enum类库

/**

* Abstract class that enables creation of PHP enums. All you

* have to do is extend this class and define some constants.

* Enum is an object with value from on of those constants

* (or from on of superclass if any). There is also

* __default constat that enables you creation of object

* without passing enum value.

*

* @author Marijan Šuflaj

* @link http://php4every1.com

*/

abstract class Enum {

/**

* Constant with default value for creating enum object

*/

const __default = null;

private $value;

private $strict;

private static $constants = array();

/**

* Returns list of all defined constants in enum class.

* Constants value are enum values.

*

* @param bool $includeDefault If true, default value is included into return

* @return array Array with constant values

*/

public function getConstList($includeDefault = false) {

$class = get_class($this);

if (!array_key_exists($class, self::$constants)) {

self::populateConstants();

}

return $includeDefault ? array_merge(self::$constants[__CLASS_], array(

"__default" => self::__default

)) : self::$constants[__CLASS_];

}

/**

* Creates new enum object. If child class overrides __construct(),

* it is required to call parent::__construct() in order for this

* class to work as expected.

*

* @param mixed $initialValue Any value that is exists in defined constants

* @param bool $strict If set to true, type and value must be equal

* @throws UnexpectedValueException If value is not valid enum value

*/

public function __construct($initialValue = null, $strict = true) {

$class = get_class($this);

if (!array_key_exists($class, self::$constants)) {

self::populateConstants();

}

if ($initialValue === null) {

$initialValue = self::$constants[$class]["__default"];

}

$temp = self::$constants[$class];

if (!in_array($initialValue, $temp, $strict)) {

throw new UnexpectedValueException("Value is not in enum " . $class);

}

$this->value = $initialValue;

$this->strict = $strict;

}

private function populateConstants() {

$class = get_class($this);

$r = new ReflectionClass($class);

$constants = $r->getConstants();

self::$constants = array(

$class => $constants

);

}

/**

* Returns string representation of an enum. Defaults to

* value casted to string.

*

* @return string String representation of this enum's value

*/

public function __toString() {

return (string) $this->value;

}

/**

* Checks if two enums are equal. Only value is checked, not class type also.

* If enum was created with $strict = true, then strict comparison applies

* here also.

*

* @return bool True if enums are equal

*/

public function equals($object) {

if (!($object instanceof Enum)) {

return false;

}

return $this->strict ? ($this->value === $object->value)

: ($this->value == $object->value);

}

}

使用示例如下：

class MyEnum extends Enum {

const HI = "Hi";

const BY = "By";

const NUMBER = 1;

const __default = self::BY;

}

var_dump(new MyEnum(MyEnum::HI));

var_dump(new MyEnum(MyEnum::BY));

//Use __default

var_dump(new MyEnum());

try {

new MyEnum("I don't exist");

} catch (UnexpectedValueException $e) {

var_dump($e->getMessage());

}

输出结果如下：

object(MyEnum)#1 (2) {

["value":"Enum":private]=>

string(2) "Hi"

["strict":"Enum":private]=>

bool(true)

}

object(MyEnum)#1 (2) {

["value":"Enum":private]=>

string(2) "By"

["strict":"Enum":private]=>

bool(true)

}

object(MyEnum)#1 (2) {

["value":"Enum":private]=>

string(2) "By"

["strict":"Enum":private]=>

bool(true)

}

string(27) "Value is not in enum MyEnum"

希望本文所述对大家PHP程序设计有所帮助。