获取字符串指定字符 前后 的字符串

public function err_redisOp()
{
$redis = new Redis();
$redis->connect(‘localhost’,6379);

    $res = $redis->hKeys('order_bc_api_err');
    $data = array_slice($res,0,5);//获取$res数组中的 前5条数据

    foreach ($data as $data_){

        $order_sn = substr($data_,0,strrpos($data_,'_+_'));//获取$data_字符串中出现 '_+_' 前的字符串
        $express_num = substr($data_,strrpos($data_,"_")+3);//获取$data_字符串中出现 '_' 后3位 的字符串
        $condition['order_sn'] = $order_sn;
        $condition['express_num'] = $express_num;
        $model_customs_order_bc = Model('customs_order_bc');
        $res = $model_customs_order_bc->getCustomsOrderInfo(array('order_sn'=>$order_sn,'express_num'=>$express_num));

        if(!empty($res)){
            $key = $order_sn.'_+_'.$express_num;
            var_dump($key);
            $res = $redis->hDel('order_bc_api_err',$key);
        }
    }
}