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 ]] )
}

<"htmlcode">

6
Value not a const in enum Month




（2）自定义的Enum类库


<"__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 "htmlcode">

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"




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