__sleep & __wakeup in PHP 5



When you serialize and unserialize a PHP object, PHP will automatically check to see if there is a __sleep or __wakeup magic method in the class (depending on weather your serializing or unserializing). 

Using __sleep

When you serialize an object, PHP automatically checks to see if the object has a __sleep magic method. The sleep method is used because you might not want to serialize the whole object, sometimes just a specific array for example.

The example below demonstrates a class that would use the __sleep method when serialized: 

class WebDeveloper { 
  $private $info = array();
  public function __set($item, $value) {
    $this->info[$item] = $value;
  public function __sleep() {
    return array(‘info’);
$developer = new WebDeveloper();
$developer->name = ‘Jordizle’;
$data = serialize($developer);

 The above code will save a serialized version of the ‘info’ array in the variables ‘data’. 

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