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。