The Serializable interface

Intro

Interface for customized serializing.

Classes that implement this interface no longer support __sleep() and __wakeup(). The serialize method is called whenever an instance needs to be serialized. This does not invoke __destruct or have any other side effect unless programmed inside the method. When the data is unserialized the class is known and the appropriate unserialize method is called as a constructor instead of calling __construct. The constructor can be called from within the unserialize method if desired.

New code should use the __serialize() and __unserialize() magic methods instead, available as of PHP 7.4.0. When a class declares both them and this interface, serialize() always uses __serialize() and never reaches Serializable::serialize. Unserializing is decided by the format of the data instead: a payload written by PHP 7.4.0 or later is read by __unserialize(), one written before it is still read by Serializable::unserialize. Implementing Serializable therefore remains of use for reading such older payloads, and for satisfying a Serializable type declaration; declaring all four methods covers every case, and avoids the deprecation notice.

Interfacesynopsis

Examples

Supporting PHP 7.1.0 through 7.3.0

The magic methods carry the serialized form, and the interface methods delegate to them, so that a single representation serves both.

<?php
class Task implements Serializable
{
    private $label;

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

    public function __serialize(): array
    {
        return ['label' => $this->label];
    }

    public function __unserialize(array $data): void
    {
        $this->label = $data['label'];
    }

    // Never called as of PHP 7.4.0
    public function serialize()
    {
        return serialize($this->__serialize());
    }

    // Still called as of PHP 7.4.0, for data written before it
    public function unserialize($data)
    {
        $this->__unserialize(unserialize($data));
    }
}

var_dump(serialize(new Task('deploy')));
?>

The above example will output:

string(40) "O:4:"Task":1:{s:5:"label";s:6:"deploy";}"

Prior to PHP 7.4.0, the same code serializes through the interface instead, and outputs string(47) "C:4:"Task":31:{a:1:{s:5:"label";s:6:"deploy";}}".

Serialize Unserialize