在我的项目中，我选择mvc编程模式。
首先，我定义了一个特定的trade类，用于从db获取数据；trade.php类的代码是：

namespace model;

class Trade Extends \Mysql\Crud {
private $ltb;

public function getLastTradeTime($uid, $ip) {
   //$params = array('uid' => '36998020','ip' => $ip);
   $sql = "SELECT sys_dateline FROM ms_trade WHERE uid=36998020 AND sys_ip='183.62.232.198' ORDER BY id DESC LIMIT 1;";
   $this->ltb = $this->getDb()->query($sql);
   return $this->ltb;// There is only one return value:1528957574
}

}

trade.php类是extends\mysql\crud类。
php类用于连接da，以及创建、更新、删除sql等。
我还专门测试了crud.php类的每个函数。
代码crud.php类是：

<?php
namespace Mysql;
class Crud {

private $db;
protected $fields;
public $variables;

public function __construct($data = array()) {
    if ($this->fields && $data) {
        foreach ($data as $k => $d) {
            if (!in_array($k, $this->fields)) {
                unset($data[$k]);
            }
        }
    }
    $this->variables  = $data;
}

public function setDb($db) {
    $this->db = $db;
}
public function getDb() {
    //connecting function
}

public function __set($name,$value){
    //set value
}

public function __get($name)
{   
    //get value
}

public function save($id = "0") {
    //for saving value
}

public function create() { 
    //for create sql
}

public function delete($id = "") {
    //for delete sql
}
}

现在我有了1.php控件页，用于通过trade.php类获取数据，

$uid = $login_userinfo['uid'];
$ip = getClientIp();
$trade_model = new \model\Trade();
$lastTrade_time = $trade_model->getLastTradeTime($uid, $ip); //the value should be 1528957574

但lasttrade的值是“array”；看来没什么问题。谁能帮我个忙。