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：
<?phpclass 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：
6Value 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 __defaultvar_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。
