The __sleep() magic method is mainly responsible of customizing the data collection while serialization of a class.

Let’s first look at a simple example on how to serialize & unserialize a class in PHP

Serialize a class

class DevPeel
{
	public $name = 'devpeel';
}

$class = new DevPeel();

var_dump(serialize($class));

Now let’s take the serialized string and try to unserialize it.

Unserialize a class

$serialized = 'O:7:"DevPeel":1:{s:4:"name";s:7:"devpeel";}';
$class = unserialize($serialized);

var_dump($class);

and the output:

object(__PHP_Incomplete_Class)#1 (2) {
  ["__PHP_Incomplete_Class_Name"]=>
  string(7) "DevPeel"
  ["name"]=>
  string(7) "devpeel"
}

Another Example (Job Dispatch)

Let’s see a simple example of serializing data of a job assigned to email user something. We’ll first serialize the data and later try to unserialize it.

class SendUserEmail
{
	protected $user;

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

	public function handle(){
		var_dump('send email');
	}
}

class User
{
	protected $data =[
		'email'=>'usama@devpeel.com'
	];

	public function __sleep(){
		return ['data'];
	}
}

$user = new User();
$job = new SendUserEmail($user);

$string = serialize($job);
var_dump($string);

& the output:

string(111) "O:13:"SendUserEmail":1:{s:7:"*user";O:4:"User":1:{s:7:"*data";a:1:{s:5:"email";s:17:"usama@devpeel.com";}}}"

If required to put this into our database, we probably need to base64_encode this string.
Now let’s convert it back using unserialize helper function, likeso

$unserialized = unserialize(base64_decode($string));

& the unserialized output:

object(SendUserEmail)#3 (1) {
  ["user":protected]=>
  object(User)#4 (1) {
    ["data":protected]=>
    array(1) {
      ["email"]=>
      string(17) "usama@devpeel.com"
    }
  }
}

Now after unserialzing, we can still access to methods of the class likeso,

$unserialized->handle();

It will run the handle() method inside of SendUserEmail class & we can carry out further processes.

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