19

<?php
highlight_file(__FILE__);

class Person
{
    public $name;
    public $id;
    public $age;

    public function __invoke($id)
    {
        $name = $this->id;
        $name->name = $id;
        $name->age = $this->name;
    }
}

class PersonA extends Person
{
    public function __destruct()
    {
        $name = $this->name;
        $id = $this->id;
        $age = $this->age;
        $name->$id($age);
    }
}

class PersonB extends Person
{
    public function __set($key, $value)
    {
        $this->name = $value;
    }
}

class PersonC extends Person
{
    public function __Check($age)
    {
        if(str_contains($this->age . $this->name,"flag"))
        {
            die("Hacker!");
        }
        $name = $this->name;
        $name($age);
    }

    public function __wakeup()
    {
        $age = $this->age;
        $name = $this->id;
        $name->age = $age;
        $name($this);
    }
}

if(isset($_GET['person']))
{
    $person = unserialize($_GET['person']);
}