OOP PHP集成mysqli_query

Question

我將編輯問題以使其更清楚，這樣您就可以看到我現在所擁有的內容，並且可以更輕松地理解問題。

<?php
$mysqli = new mysqli("localhost", "user", "password", "test");
class building
{
private $mysqli;
public $buildingid;
public $userid;
public $buildinglevel;




public function __construct($buildingid, $userid, \mysqli $mysqli)
{
    $this->buildinglevel;
    $this->mysqli = $mysqli;
}

public function getLevel()
{
    return $this->mysqli->query("SELECT ".$this->buildingid." FROM worlds WHERE city_userid=".$this->userid."");
}
}

}
?>

然后，我用它來創建和使用函數：

$cityHall = new building("cityHall",$user['id'],$mysqli);
echo $cityHall->getLevel();

結果空白，什么也沒有發生。

Answer 1

您應該將mysqli實例注入到建築類的__construct（）中：

$ mysqli =新的mysqli（'user'，'password'，'localhost'，'test'）;

如果（$ mysqli-> connect_errno）{printf（“連接失敗：％s \\ n”，$ mysqli-> connect_error）; }

class building
{
private $mysql;
private $buildingid;
private $userid;

// I need to have a mysqli_query here to get the info for the correct building, 
//to be able to set the "buildinglevel" for each object from the MYSQL DB, seems basic   
//but none of the things ive tried has worked.


public function __construct($buildingid, $userid, $mysqli)
{
    $this->buildinglevel;
    $this->mysqli = $mysqli;
    $this->userid = (int)$userid;
    $this->buildingid= (int)$buildingid;
}

public function getLevel()
{
    $query = $this->mysqli->query("SELECT ".$this->buildingid." FROM worlds WHERE city_userid=".$this->userid);
    $row = $query->fetch_assoc();
    if (!$query) {
        return $this->mysqli->error;
    }
    if ($query->num_rows == 0) {
        return 'no database records found';
    }

    return $row;
}

}

$Bulding = new building("cityHall", $user['id'], $mysqli);
$level = $Bulding->getLevel();
var_dump($level);

Answer 2

對象是封裝行為的單元，這些行為通過方法暴露給其他對象。 從數據庫檢索到的公共屬性的包裝器不是面向對象的編程工具。 實際上， mysqli可以通過fetch_object為您完成此fetch_object ：

$result = $mysqli->query($query);
while ($building = $result->fetch_object()) {
    // access properties via $building->buildingid, etc.
}

除非building類實際上通過方法提供功能並實現某種抽象，否則不需要它。 相反，您可以使用包裝數據庫（ mysqli ）的DAO（數據訪問對象），並且其檢索的數據由模型使用。

interface Dao {
    public function get($id);
}

class BuildingDao implements Dao {
    // DB can be a wrapper for mysqli
    // but servers as an interface so it
    // can be replaced easily
    public function __construct(DB $db) {
        $this->db = $db;
    }

    public function get($id) {
        return $this->db->prepare(
            "SELECT buildinglevel FROM building WHERE buildingid = ?"
        )->execute($id)->fetch();
    }
}

Answer 3

您的類似乎就是所謂的模型：它代表某種形式的數據，在您的情況下是特定的建築物。

一種方法是將MySQLi對象作為構造函數對象以及要查詢的建築物的ID傳遞，並將結果分配給類屬性。 如下所示：

<?php
class Building
{
    private $db;

    protected $id;
    protected $level;

    public function __construct(mysqli $db, $id = null)
    {
        $this->db = $db;

        if (!is_null($id) && intval($id) > 0) {
            $stmt = $this->db->prepare("SELECT buildingid, buildinglevel FROM building WHERE `id` = ?");
            $stmt->bind_param('i', $id);
            $stmt->execute();
            $stmt->bind_result($this->id, $this->level);
            $stmt->fetch();
        }
    }

    public function getId()
    {
        return (int)$this->id;
    }

    public function getLevel()
    {
        return (int)$this->level;
    }
}

然后，您可以按以下方式獲取建築物的屬性：

$building = new Building($mysqli, 1);

printf('Building ID is %d and building level is %d', $building->getId(), $building->getLevel());