Detaillierte Erläuterung von Beispielen für Überladung und magische Methoden in PHP

class Foo {    
private $name;    
private $link;    
public function construct($name) {        
$this->name = $name;
    }    
    public function destruct() {        
    echo 'Destroying: ', $this->name, PHP_EOL;//PHP_EOL代表php的换行符    }
}

<?php
class PropertyTest {
     /**  被重载的数据保存在此  */
    private $data = array();

 
     /**  重载不能被用在已经定义的属性  */
    public $declared = 1;

     /**  只有从类外部访问这个属性时，重载才会发生 */
    private $hidden = 2;

    public function set($name, $value) 
    {
        echo "Setting &#39;$name&#39; to &#39;$value&#39;\n";
        $this->data[$name] = $value;
    }


    public function get($name) 
    {
        echo "Getting &#39;$name&#39;\n";
        if (array_key_exists($name, $this->data)) {
            return $this->data[$name];
        }

        $trace = debug_backtrace();
        trigger_error(
            &#39;Undefined property via get(): &#39; . $name .
            &#39; in &#39; . $trace[0][&#39;file&#39;] .
            &#39; on line &#39; . $trace[0][&#39;line&#39;],
            E_USER_NOTICE);
        return null;
    }



    /**  PHP 5.1.0之后版本 */
    public function isset($name) 
    {
        echo "Is &#39;$name&#39; set?\n";
        return isset($this->data[$name]);
    }

    /**  PHP 5.1.0之后版本 */
    public function unset($name) 
    {
        echo "Unsetting &#39;$name&#39;\n";
        unset($this->data[$name]);
    }

    /**  非魔术方法  */
    public function getHidden() 
    {
        return $this->hidden;
    }
}


echo "<pre class="brush:php;toolbar:false">\n";

$obj = new PropertyTest;

$obj->a = 1;
echo $obj->a . "\n\n";

var_dump(isset($obj->a));
unset($obj->a);
var_dump(isset($obj->a));
echo "\n";

echo $obj->declared . "\n\n";

echo "Let&#39;s experiment with the private property named &#39;hidden&#39;:\n";
echo "Privates are visible inside the class, so get() not used...\n";
echo $obj->getHidden() . "\n";
echo "Privates not visible outside of class, so get() is used...\n";
echo $obj->hidden . "\n";
?>

<?php
class Connection 
{
    protected $link;
    private $server, $username, $password, $db;
    
    public function construct($server, $username, $password, $db)
    {
        $this->server = $server;
        $this->username = $username;
        $this->password = $password;
        $this->db = $db;
        $this->connect();
    }
    
    private function connect()
    {
        $this->link = mysql_connect($this->server, $this->username, $this->password);
        mysql_select_db($this->db, $this->link);
    }
    
    public function sleep()
    {
        return array(&#39;server&#39;, &#39;username&#39;, &#39;password&#39;, &#39;db&#39;);
    }
    
    public function wakeup()
    {
        $this->connect();
    }
}
?>

<?php
class SubObject
{
    static $instances = 0;
    public $instance;

    public function construct() {
        $this->instance = ++self::$instances;
    }

    public function clone() {
        $this->instance = ++self::$instances;
    }
}

class MyCloneable
{
    public $object1;
    public $object2;

    function clone()
    {
      
        // 强制复制一份this->object， 否则仍然指向同一个对象
        $this->object1 = clone $this->object1;
    }
}

$obj = new MyCloneable();

$obj->object1 = new SubObject();
$obj->object2 = new SubObject();

$obj2 = clone $obj;


print("Original Object:\n");
print_r($obj);

print("Cloned Object:\n");
print_r($obj2);

?>