php中關係數組處理

<?php
//$a爲車子的名稱
//$b爲車子的型號
//需要實現把車子的型號放到車子名字下，關聯字段$b中的pid對應$a中的id
$a = [
    ['id' => 1, 'name' => '奧迪'],
    ['id' => 2, 'name' => '奔馳'],
    ['id' => 3, 'name' => '瑪莎拉蒂']
];
$b = [
    ['id' => 1, 'name' => 'A4', 'pid' => 1],
    ['id' => 2, 'name' => 'A6', 'pid' => 1],
    ['id' => 3, 'name' => 'S600', 'pid' => 2]
];
foreach ($a as $k => $v) {
    $info = [];
    foreach ($b as $kk => $vv) {
        if ($vv['pid'] == $v['id']) {
            $info[] = $vv;
        }
    }
    $a[$k]['extra'] = $info;
}
echo "<pre>";
var_dump($a);
?>