OOP數據庫連接/斷開類

Question

我剛剛開始學習面向對象編程的概念，並將一個類連接到數據庫，選擇數據庫並關閉數據庫連接。到目前爲止，除了關閉與數據庫的連接外，一切似乎都行得通。

class Database { 

    private $host, $username, $password; 
    public function __construct($ihost, $iusername, $ipassword){ 
     $this->host = $ihost; 
     $this->username = $iusername; 
     $this->password = $ipassword; 
    } 
    public function connectdb(){ 
     mysql_connect($this->host, $this->username, $this->password) 
      OR die("There was a problem connecting to the database."); 
     echo 'successfully connected to database<br />'; 
    } 
    public function select($database){ 
     mysql_select_db($database) 
      OR die("There was a problem selecting the database."); 
     echo 'successfully selected database<br />'; 
    } 
    public function disconnectdb(){ 
     mysql_close($this->connectdb()) 
      OR die("There was a problem disconnecting from the database."); 
    } 
} 

$database = new database('localhost', 'root', 'usbw'); 
$database->connectdb(); 
$database->select('msm'); 
$database->disconnectdb(); 

當我試圖從數據庫中，我得到了以下錯誤消息斷開：

Warning: mysql_close(): supplied argument is not a valid MySQL-Link resource in F:\Programs\webserver\root\oop\oop.php on line 53 

我猜它並不像放置connectdb方法mysql_close的括號內爲簡單功能，但無法找到正確的方法來做到這一點。

感謝

Answer 1

我會添加一個連接/鏈接變量到你的類，並使用析構函數。 這也可以幫助您避免關閉連接，導致連接自動完成。
這是你需要傳遞給你的mysql_close（）的$ this->鏈接。

class Database { 

    private $link; 
    private $host, $username, $password, $database; 

    public function __construct($host, $username, $password, $database){ 
     $this->host  = $host; 
     $this->username = $username; 
     $this->password = $password; 
     $this->database = $database; 

     $this->link = mysql_connect($this->host, $this->username, $this->password) 
      OR die("There was a problem connecting to the database."); 

     mysql_select_db($this->database, $this->link) 
      OR die("There was a problem selecting the database."); 

     return true; 
    } 

    public function query($query) { 
     $result = mysql_query($query); 
     if (!$result) die('Invalid query: ' . mysql_error()); 
     return $result; 
    } 

    public function __destruct() { 
     mysql_close($this->link) 
      OR die("There was a problem disconnecting from the database."); 
    } 

} 

實例應用：

<?php 
    $db = new Database("localhost", "username", "password", "testDatabase"); 

    $result = $db->query("SELECT * FROM students"); 

    while ($row = mysql_fetch_assoc($result)) { 
     echo "First Name: " . $row['firstname'] ."<br />"; 
     echo "Last Name: " . $row['lastname'] ."<br />"; 
     echo "Address: " . $row['address'] ."<br />"; 
     echo "Age: "  . $row['age']  ."<br />"; 
     echo "<hr />"; 
    } 
?> 

編輯：
所以人們可以實際使用的類，我添加缺少的屬性/方法。
下一步是擴展查詢方法，包括防止注入和其他輔助函數。
我做了以下修改：

• 添加缺少的私有財產
• 新增__construct（$主機，$的用戶名，$密碼，$數據庫）
• 合併connectdb（）和select（）爲__construct （）保存額外的兩行代碼。
• 新增查詢（$查詢）
• 使用示例

如有我犯了一個錯字或錯誤，留下一個建設性的意見，這樣我就可以修復它爲別人着想。

Answer 2

你不從connectdb()返回任何東西。但你通過這個函數的返回到mysql_close()。

Answer 3

mysql_close需要一個參數來斷開連接，但是你什麼也沒有提供。

 

class Database { 

    private $host, $username, $password, $con; 

    public function __construct($ihost, $iusername, $ipassword){ 
     $this->host = $ihost; 
     $this->username = $iusername; 
     $this->password = $ipassword; 
     $this->con = false; 
    } 


    public function connect() { 
     $connect = mysql_connect($this->host, $this->username, $this->password); 
     return $connect; 
    } 


    public function connectdb(){ 
     $conn = $this->connect(); 
     if($conn) 
     { 
      $this->con = true; 
      echo "Successsfully Connected. 
"; 
      return true; 
     } 
     else { 
      echo "Sorry Could Not Connect. 
"; 
      return false; 
     } 
    } 


    public function select($database){ 
     if($this->con) 
     { 
      if(mysql_select_db($database)) 
      { 
       echo "Successfully Connected Database. $database. 
"; 
       return true; 
      } 
      else 
      { 
       echo "Unknown database. 
"; 
      } 
     } 
     else { 
      echo "No active Connection. 
"; 
      return false; 
     } 
    } 


    public function disconnectdb(){ 
     if($this->con) 
     { 
      if(mysql_close($this->connect())) 
      { 
       $this->con = false; 
       echo "Successfully disconnected. 
"; 
       return true; 
      } 
     } 
     else 
     { 
      echo "Could Not disconnect. 
"; 
      return false; 
     } 
    } 

} 

    $database = new database('localhost', 'root', ''); 
    $database->connectdb(); 
    $database->select('databaseoffacebook'); 
    $database->disconnectdb(); 

Answer 4

您應該意識到，mysql_*功能是在PHP 4中引入的，該功能早於1年前。這個API是非常古老的，並且該過程已經開始實際上deprecating this extension。

你不應該在2012年用mysql_*函數寫新代碼。

存在兩個很好的替代方案：PDO和MySQLi。這兩種方法都是用面向對象的代碼編寫的，而且它們還使您能夠使用prepared statements。

那比如你在PDO寫是這樣的原帖表明：

//connect to the the database 
$connection = new PDO('mysql:host=localhost;dbname=msm', 'username', 'password'); 
//disconnects 
$connection = null; 

當然也有較爲複雜的情況，但問題的立場 - 時間去發展。

Answer 5

面向對象編程適用於PDO和mysqli。試一試

Answer 6

<?php 

class Database{ 

    private $link; 
    //private $host,$username,$password,$database; 
    //private $status; 

    public function __construct(){ 

     $this->host   = 'localhost'; 
     $this->username  = 'root'; 
     $this->password  = ''; 
     $this->database  = 'workclass'; 

     $this->link = mysqli_connect($this->host,$this->username,$this->password); 

     $this->status = mysqli_select_db($this->link,$this->database); 

     if (!$this->status) { 
      return $this->status="Failed to Connected with Database"; 
     }else{ 
      return $this->status="Database is connected"; 
     } 
    } 
} 

$object = new Database(); 

echo $object->status; 

?>