PHPオブジェクトにおける、シャローコピーとディープコピー

deep_copy.php

<?php
class Player extends stdClass
{
    public function __clone()
    {
        $this->status = clone $this->status;
    }
}

$player = new Player();
$status = new stdClass();
$status->level = 35;

$player->name = 'ポカパマズ';
$player->status = $status;

$player2 = clone $player;

var_dump($player->name, $player->status->level);
var_dump($player2->name, $player2->status->level);
echo PHP_EOL;

// $player の 値を変更する
$player->name = 'オルテガ';
$player->status->level = 52;

var_dump($player->name, $player->status->level);
var_dump($player2->name, $player2->status->level);

deep_copy_result.txt

string(15) "ポカパマズ"
int(35)
string(15) "ポカパマズ"
int(35)

string(12) "オルテガ"
int(52)
string(15) "ポカパマズ"
int(35)

shallow_copy.php

<?php
$player = new stdClass();
$status = new stdClass();
$status->level = 35;

$player->name = 'ポカパマズ';
$player->status = $status;

$player2 = clone $player;

var_dump($player->name, $player->status->level);
var_dump($player2->name, $player2->status->level);
echo PHP_EOL;

// $player の 値を変更する
$player->name = 'オルテガ';
$player->status->level = 52;

// オルテガだけ変えたつもりなのにポカパマズもレベル52になってしまう
var_dump($player->name, $player->status->level);
var_dump($player2->name, $player2->status->level);

shallow_copy_result.txt

string(15) "ポカパマズ"
int(35)
string(15) "ポカパマズ"
int(35)

string(12) "オルテガ"
int(52)
string(15) "ポカパマズ"
int(52)