使用單例類在php中建立數據庫連接

Question

任何人都可以請示例代碼來指導我使用單例類在php中建立數據庫連接。

Answer 1

class DatabaseSingleton 
{ 
    // [Singleton] 
    private static $instance = null; 
    public static function getInstance() 
    { 
    if (!self::$instance) 
    { 
     self::$instance = new self(); 
    } 
    return self::$instance; 
    } 
    private function __clone(){} 
    // [/Singleton] 

    private $connection = null; 

    private function __construct() 
    { 
    $this->connection = mysql_connect('localhost','root','admin'); 
    if ($this->connection) 
    { 
     mysql_select_db('my_database'); 
    } 
    } 

    // 
    // crud operations go here. 
    // 
} 

$db = DatabaseSingleton::getInstance(); 
$db->SomeCRUDOperation(); 

也許這樣的事？非常基本，但應該給你一個出發點。

Answer 2

這是一個單例模式的樣子：

<?php 
class SingletonClass 
{ 
    static private $instance = null; 

static public function getInstance() 
{ 
    if (null === self::$instance) { 
     self::$instance = new self; 
    } 
    return self::$instance; 
} 

private function __construct(){} 
private function __clone(){} 


} 

$singletonClass = SingletonClass::getInstance(); 

現在你可以把隨機的功能和參數在那裏處理您的DB-東西。我希望能回答你的問題。

Answer 3

請參閱用戶手冊上如何實現Singleton模式的一個例子：http://www.php.net/manual/en/language.oop5.patterns.php

然後，只需建立你的類構造函數的數據庫連接。

Answer 4

我用的是這樣的：

class DBConn 
    { 
     static private $_db = null; // The same PDO will persist from one call to the next 
     private function __construct() {} // disallow calling the class via new DBConn 
     private function __clone() {} // disallow cloning the class 
     /** 
     * Establishes a PDO connection if one doesn't exist, 
     * or simply returns the already existing connection. 
     * @return PDO A working PDO connection 
     */ 
     static public function getConnection() 
     { 
      if (self::$_db == null) { // No PDO exists yet, so make one and send it back. 
       try { 
        self::$_db = new PDO('mysql:host=' . DB_HOST . ';dbname=' . DB_NAME, DB_USER, DB_PASS); 
       } catch (PDOException $e) { 
        // Use next line for debugging only, remove or comment out before going live. 
        // echo 'PDO says: ' . $e->getMessage() . '<br />'; 
        // This is all the end user should see if the connection fails. 
        die('<h1>Sorry. The Database connection is temporarily unavailable.</h1>'); 
       } // end PDO connection try/catch 
       return self::$_db; 
      } else { // There is already a PDO, so just send it back. 
       return self::$_db; 
      } // end PDO exists if/else 
     } // end function getConnection 
    } // end class DBConn 


    /** 
    * And you can use it as such in a class 
    * */ 

    class Post { 
     public function __construct(){ 
      $this->db = DBConn::getConnection(); 
     } 
     public function getPosts() 
     { 
      try { 
       /*** The SQL SELECT statement ***/ 
       $sql = "SELECT * FROM posts"; 
       foreach ($this->_dbh->query($sql) as $row) { 
        var_dump($row); 
       } 
       /*** close the database connection ***/ 
       $this->_dbh = null; 
      } catch (PDOException $e) { 
       echo $e->getMessage(); 
      } 
     } 
    } 

Answer 5

我使用類似下面

class Database 

{ 

private $_connection; 

    private static $_instance; //The single instance 

    private $_host = "HOST"; 

    private $_username = "USERNAME"; 
    private $_password = "PASSWORd"; 
    private $_database = "DATABASE"; 


    public static function getInstance() { 
     if(!self::$_instance) { // If no instance then make one 
      self::$_instance = new self(); 
     } 
     return self::$_instance; 
    } 

    private function __construct() { 
     $this->_connection = new mysqli($this->_host, $this->_username, 
      $this->_password, $this->_database); 

     // Error handling 
     if(mysqli_connect_error()) { 
      trigger_error("Failed to conencto to MySQL: " . mysqli_connect_error(), 
       E_USER_ERROR); 
     } 
    } 

    // Magic method clone is for prevent duplication of connection 
    private function __clone() { } 

    public function getConnection() { 
     return $this->_connection; 
    } 

} 


$db = Database::getInstance(); 

$mysqli = $db->getConnection(); 

$sql_query = "SELECT foo FROM etc"; 

$result = $mysqli->query($sql_query);