serialize.php

<?php

class Foo implements Serializable
{
  public $foo, $bar;
  
  public function serialize()
  {
    return json_encode(['foo' => $this->foo, 'bar' => $this->bar]);
  }
  
  public function unserialize($data)
  {
    $data = json_decode($data, true);
    
    $this->foo = $data['foo'];
    $this->bar = $data['bar'];
  }
}

$foo = new Foo;
$foo->foo = ['bar' => 'baz'];
$foo->bar = 'baz';

var_dump($foo, $s = serialize($foo), unserialize($s));