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PHP的Enum（枚举）的实现

作者：佚名      php网站开发编辑：admin      更新时间：2022-07-23

原文地址：http://www.cnblogs.com/zsxfbj/p/php_enum.html

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：

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1 2 3 4 5 6 7 8 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：

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 <?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：

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1 2 6 Value not a const in enum Month

 

（2）自定义的Enum类库

摘自http://www.php4every1.com/scripts/php-enum/

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 <?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 <[email protected]&gt  * @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：

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 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：

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 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"