PHP中的幻术变量小结

PHP中的魔术变量小结
PHP中，有不少很好用的魔术变量，用好之，能事半功倍，下面小结之：

1 _LINE_
  显示当前代码的行数：
  echo "This is line number : ". __LINE__;

2 _FILE_
   显示当前文件的路径

3 _METHOD_
   显示当前方法的名，比如
   class Magicconstant
{
    function __construct()
    {
      echo "This is function a";
    }
    function b()
   {
     echo "
";
     echo "This is function b";
     echo "
";
     echo __METHOD__;
   }
}
$cm = new Magicconstant();
$cm->b();

显示
   This is function a
  This is function b
  Magicconstant::b

4 _FUNCTION_
   显示当前所在函数的名
  function b()
  {
  echo "
";
echo "This is function b";
echo "
";
echo __FUNCTION__;
  }
输出：
   This is function b
Magicconstant::b

5 _DIR_
   显示当前目录名，如
  echo "The directory name is : ". __DIR__;
输出：
  The directory name is : D:\wamp\www

6 _CLASS_
   显示当前的类
class Magicconstant
{
function __construct()
{
echo "The class name is : ".__CLASS__;
}
}
$cm = new Magicconstant();
  显示：
  The class name is : Magicconstant

7 _NAMESPACE_
   显示当前命名空间
namespace MagicConstant
{
   echo "The namespace is : ".__NAMESPACE__;
}
输出：
  The namespace is : MagicConstant

8 _sleep_
  _sleep_用在将类序列化之前，
class User
{
public $userName = '';
public $userAddress = '';
public $userPhone = '';

public function setName($name='')
{

$this->userName = $name;
}

function setAddress($address='')
{
$this->userAddress = $address;
}

function setPhone($phone='')
{
$this->userPhone = $phone;
}

function __sleep()
{
return array('userAddress','userPhone');
                        // This will serialize only address and Phone number but not Name
}

}
?>
$User = new User();
$User->setName('Avinash');
$User->setAddress('Address Here');
$User->setPhone('1234567890');

$serialData = serialize($User);
echo $serialData;
?>

OutPut: O:4:"User":2:{s:11:"userAddress";s:12:"Address Here";s:9:"userPhone";s:10:"1234567890";}

程序运行时, serialize() 检查类中是否有 __sleep() ,如果有，则该函数将在任何序列化之前运行. 该函数必须返回一个需要进行序列化保存的成员属性数组，并且只序列化该函数返回的这些成员属性. 该函数有两个作用: 第一. 在序列化之前,关闭对象可能具有的任何数据库连接等. 第二. 指定对象中需要被序列化的成员属性,如果某个属性比较大而不需要储存下来,可以不把它写进__sleep()要返回的数组中,这样该属性就不会被序列化


又如：
class Test {

public $mySecret; //我的秘密不想让人知道

public function __construct($secret) {

$this->mySecret = $secret;

}

public function __sleep() {

$this->mySecret = "你休想知道我的秘密!";

return array('mySecret'); //一定要返回变量，不然返回的是个空，所以序列化也就没有东西了。

}

}

$test = new Test("我的心里话 我爱某某某");

echo serialize($test); //输出 O:4:"Test":1:{s:8:"mySecret";s:28:"你休想知道我的秘密!";}


_wakeup_
用在反序列化时：
class User
{
public $userName = '';
public $userAddress = '';
public $userPhone = '';

public function setName($name='')
{

$this->userName = $name;
}

function setAddress($address='')
{
$this->userAddress = $address;
}

function setPhone($phone='')
{
$this->userPhone = $phone;
}

function __sleep()
{
return array('userAddress','userPhone');
                       // This will serialize only address and Phone number but not Name
}

function __wakeup()
{
echo "In Wakeup function"."
";
}

}
?>
$User = new User();
$User->setName('Avinash');
$User->setAddress('Address Here');
$User->setPhone('1234567890');

$serialData = serialize($User);
echo $serialData;
echo "
";
var_dump(unserialize($serialData));
?>

Output:
In Wakeup function
object(User)#2 (3) {
  ["userName"]=>
  string(0) ""
  ["userAddress"]=>
  string(12) "Address Here"
  ["userPhone"]=>
  string(10) "1234567890"
}