PHP幻术方法小结1

PHP魔术方法小结1
PHP中除了有大量的魔术变量外,还有很多_开头的魔术方法,本文简单小结下:

1 _construct 和_destruct就不说了,构造和析构.

2 _call和_callStatic
  例子:
    class myClass() {
    private $a = true;
  }

  $myObj = new myClass();
  $myObj->showValue();

  ?>
   这里会说出错,那当然的,没定义.可以用
  class Greetings {
    function __call( $functionName, $argumentsArray ) {
      echo "Hello, " . ucfirst( $functionName ) . " !!!";
    }
  }
  $sayHello = new Greetings();
_CALL会在调用没有定义任何方法时触发

还有_callStatic
  class Greetings {
    static function __callStatic( $functionName, $argumentsArray ) {
      echo "Hello, " . ucfirst( $functionName ) . " !!!";
    }
  }

  Greetings::steve();
 

3 _set和_get
   这个是强制在类中声明的变量才能被使用,一个例子:
class myClass {
private $onlyDataMember = 0;
}
$classObj = new myClass();
$classObj->undefinedDataMember = 'Some Value';
echo $classObj->undefinedDataMember;
?>
  这个是直接输出了没定义的值,不大好,可以改成这样,强制性地:
class myClass {
private $onlyDataMember = 0;

function __set( $dataMemberName, $dataMemberValue ) {
throw new Exception( "Object property $dataMemberName is not writable!" );
}

function __get( $dataMemberName ) {
throw new Exception( "Object property $dataMemberName is not defined!" );
}
}

再来一个例子:
class UserInfo2{

   private $aData = array();

}

$oUserInfo2 = new UserInfo2;

$oUserInfo2->aData['UserName'] = '木目子';

$oUserInfo2->aData['PassWord'] = '123456';

$oUserInfo2->aData['Birthdat'] = '1978-08-16';

echo "用户名：".$oUserInfo2->aData['UserName'] ."
\n";

echo "密   码：".$oUserInfo2->aData['PassWord'] ."
\n";

echo "生   日：".$oUserInfo2->aData['Birthday'] ."
\n";

显然，这段代码会出错的，因为aData是UserInfo的私有属性，不能直接在外部使用，那现在问题是必须要给aData进行付值，这个时候__set和__get就排上用场了：

class UserInfo3{

   //private $aData = array();

   private $aData = array();

   function __set($property,$value){

     $this->aData[$property] = $value;

   }

   function __get($property){

     return $this->aData[$property];

   }

}

$oUserInfo3 = new UserInfo3;

$oUserInfo3->aData['UserName'] = '木目子';

$oUserInfo3->aData['PassWord'] = '123456';

$oUserInfo3->aData['Birthdat'] = '1978-08-16';

echo "用户名：".$oUserInfo3->aData['UserName'] ."
\n";

echo "密   码：".$oUserInfo3->aData['PassWord'] ."
\n";

echo "生   日：".$oUserInfo3->aData['Birthday'] ."
\n";




$classObj = new myClass();
$classObj->undefinedDataMember = 'Some Value';
echo $classObj->undefinedDataMember;

?>
  这样当调用的时候,就强制报错了

4) _invoke
  把对象当函数用,典型的例子为,平常我们一般这样用:
class myDbUsersClass {
private $recordsArray = array();

function __construct( $fetchThisMuchUsers ) {
// code for fetching $fetchThisMuchUsers number of records from database and store them to $recordsArray.
}

function getUsers() {
return $recordsArray;
}
}

$classObj = new myDbUsersClass( 10 );
$users = $classObj->getUsers();
foreach( $users as $user ) {
echo $user[ 'userName' ] . '
';
}
?>
现在可以这样用:
class myDbUsersClass {
private $recordsArray = array();

function __construct( $fetchThisMuchUsers ) {
// code for fetching $fetchThisMuchUsers number of records from database and store them to $recordsArray.
}

function __invoke( $onlyArgumentItAccepts ) {
return $recordsArray;
}
}

$classObj = new myDbUsersClass( 10 );
foreach( $classObj() as $user ) {
echo $user[ 'userName' ] . '
';
}
?>