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：

<?php 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

<?php /** * 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 <msufflaj32@gmail.com> * @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。