二维数组重复合并 并计算

<?php
error_reporting(0);   //5.6需要 7以上不需要
$res = [
    [
        'name'   => 'a',
        'age'    => 12,
        'number' => 11,
        'score'  => 50,
    ],
    [
        'name'   => 'a',
        'age'    => 12,
        'number' => 11,
        'score'  => 30,
    ],
    [
        'name'   => 'b',
        'age'    => 12,
        'number' => 12,
        'score'  => 50,
    ]
];
$new_arr = [];
foreach ($res as $index => $item) {
    $tmp = $item['name'] . '-' . $item['age'];
    $new_arr[$tmp]['name'] = $item['name'];
    $new_arr[$tmp]['age'] = $item['age'];
    $new_arr[$tmp]['score'] += $item['score'] . ',';
    //$res[$index]['score'] = rtrim($new_arr[$tmp]['score'],',');
}
var_dump(array_values($new_arr));
//var_dump($res);