php教程之魔术方法的使用示例(php魔术函数)

代码如下:
/** PHP把所有以__（两个下划线）开头的类方法当成魔术方法。所以你定义自己的类方法时，不要以 __为前缀。 * */

// __toString、__set、__get__isset()、__unset()
/*
  The __toString method allows a class to decide how it will react when it is converted to a string.
  __set() is run when writing data to inaccessible members.
  __get() is utilized for reading data from inaccessible members.
  __isset() is triggered by calling isset() or empty() on inaccessible members.
  __unset() is invoked when unset() is used on inaccessible members.
 */
class TestClass {

    private $data = array();
    public $foo;

    public function __construct($foo) {
        $this->foo = $foo;
    }

    public function __toString() {
        return $this->foo;
    }

    public function __set($name, $value) {
        echo "__set, Setting '$name' to '$value'/n";
        $this->data[$name] = $value;
    }

    public function __get($name) {
        echo "__get, Getting '$name'/n";
        if (array_key_exists($name, $this->data)) {
            return $this->data[$name];
        }
    }

    /** As of PHP 5.1.0 */
    public function __isset($name) {
        echo "__isset, Is '$name' set?/n";
        return isset($this->data[$name]);
    }

    /** As of PHP 5.1.0 */
    public function __unset($name) {
        echo "__unset, Unsetting '$name'/n";
        unset($this->data[$name]);
    }

}

$obj = new TestClass('Hello');
echo "__toString, $obj/n";
$obj->a = 1;
echo $obj->a . "/n/n";
var_dump(isset($obj->a));
unset($obj->a);
var_dump(isset($obj->a));
echo "/n/n";
/**
  输出结果如下：
  __toString, Hello
  __set, Setting 'a' to '1'
  __get, Getting 'a'
  __isset, Is 'a' set?
  bool(true)
  __unset, Unsetting 'a'
  __isset, Is 'a' set?
  bool(false)
 **/

// __call  __callStatic
/*
  mixed __call ( string $name , array $arguments )
  mixed __callStatic ( string $name , array $arguments )
  __call() is triggered when invoking inaccessible methods in an object context.