php过滤数组

$str='PC,ANDROID';

$res=[['from_platform'=>'PC','user_num'=>200],['from_platform'=>'ANDROID','user_num'=>100],['from_platform'=>'IOS','user_num'=>400]];
要实现的结果：

Array
(
[0] => Array
(
[from_platform] => PC
[user_num] => 200
)

[1] => Array
(
[from_platform] => ANDROID
[user_num] => 100
)

)

代码：

$filter_arr=array_filter($res,function($item) use($str) {
    if($str){
        $str=str_replace('，',',',$str);
        $str_arr=explode(',',$str);
        return in_array($item['from_platform'],$str_arr);
    }else{
        return  true;
    }
});

$filter_arr就是返回的结果数组