PHP Class - 如何只连接一次数据库

Question

我试着做一个简单的SQLclass。只有一个问题：

function __classDBREAD($table, $where, $value, $back)
{
    $link = mysql_connect('127.0.0.1','XXXX','XXXXXX');
    mysql_select_db('XXXX', $link);
    mysql_set_charset('utf8');

    $sql = "SELECT * FROM $table WHERE $where = '$value' LIMIT 1";
    $result = mysql_query($sql, $link) or die(mysql_error());
    $row = mysql_fetch_assoc($result);
    return $row[$back];
    mysql_close($link);
}

现在，我怎样才能只连接到 SQL 一次并添加诸如“dbUpdate”、“dbInsert”和“dbRead”之类的函数而不是每次都连接到数据库？

teamspeak 连接也是如此。

举个例子：

require_once                      ("lib/TeamSpeak3/TeamSpeak3.php");
    $ts3_VirtualServer              = TeamSpeak3::factory("serverquery://XXXXX:XXXX@127.0.0.1:10011/?server_port=XXXX");
    $__varTeamspeakClients          = $ts3_VirtualServer->clientList();
    $__intTeamspeakClientsOnline    = $ts3_VirtualServer["virtualserver_clientsonline"] - 1;
    $ts3_VirtualServer->request('clientupdate client_nickname='.$this->__classRndString(8));

同样的问题。当我在页面中包含 Class 时，如何只定义一次连接？

Answer 1

首先，您根本不应该使用 mysql_* 函数。它们已被弃用并且使用起来很危险。但是假设地，你可以使用全局变量。

在函数外部（在全局范围内）定义您的连接，然后使用 global 为您的函数提供访问权限。现在您所要做的就是在所有需要它的函数中包含这一 "global" 行。

$link = mysql_connect('127.0.0.1','XXXX','XXXXXX');

function __classDBREAD($table, $where, $value, $back)
{
    global $link;
    mysql_select_db('XXXX', $link);
    mysql_set_charset('utf8');

    $sql = "SELECT * FROM $table WHERE $where = '$value' LIMIT 1";
    $result = mysql_query($sql, $link) or die(mysql_error());
    $row = mysql_fetch_assoc($result);
    return $row[$back];
    mysqli_close($link);
}

编辑...

我没有仔细阅读。我看到您正在处理 class，因此全局变量不是最佳选择。考虑这个..

class mydbclassthing {
    private $conn;
    public function __construct(){
        $this->conn = mysql_connect('127.0.0.1','XXXX','XXXXXX');
    }

    function __classDBREAD($table, $where, $value, $back)
    {
        $link = $this->con;
        mysql_select_db('XXXX', $link);
        mysql_set_charset('utf8');

        $sql = "SELECT * FROM $table WHERE $where = '$value' LIMIT 1";
        $result = mysql_query($sql, $link) or die(mysql_error());
        $row = mysql_fetch_assoc($result);
        return $row[$back];
        mysql_close($link);
    }
}

Answer 2

正如 PHP 文档所说的有关持久数据库连接 (http://php.net/manual/en/features.persistent-connections.php) 的内容：

an instance of the PHP interpreter is created and destroyed for every page request (for a PHP page) to your web server. Because it is destroyed after every request, any resources that it acquires (such as a link to an SQL database server) are closed when it is destroyed. In this case, you do not gain anything from trying to use persistent connections -- they simply don't persist.

如果您想要更有效地重用代码，那么以 OOP 方式进行是关键。

我以后可能会想到更好的解决方案，但我会做的是使用class成员将link存储到SQL，所以他们没有每次创建：

class MySQL {

    protected $mysql_link;
    protected $server = '127.0.0.1'; //and so on...

    public function __construct() {
       $this->link = mysql_connect($this->server,$this->user,$this->password);
       mysql_select_db($this->selected_db, $this->link);
       mysql_set_charset('utf8');
    }

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

    public function close() {
        return mysql_close($this->link);
    }

}

现在，在您的应用程序的其余部分使用 OOP（类似于依赖注入）会很棒，但如果不是，无论如何，您总是可以实例化您正在创建的 class 甚至存储该对象在 $_SESSION 变量中。

使用 $object->link() 将始终 return 该实例的 link，而不是每次需要执行任何查询时都创建新实例，

Answer 3

既然大家都在往环里扔自己的OOP（注意：我准备做PDO因为我比较懂，不过原理是一样的，只是代入连接）:

<?php
class DatabaseConnection
    {
        # Create a singleton to store the connection for reuse
        private static $singleton,
                       $con;
        # save connection to singleton and return itself (the full object)
        public function __construct()
           {
                # If your singleton is not set
                if(!isset(self::$singleton))
                    # assign it this class
                    self::$singleton = $this;
                # return this class
                return self::$singleton;
           }
        # This is a connection method because your __construct
        # is not able to return the $pdo connection
        public function connection($host='hostname',$username='username',$password='password',$database='database')
            {
                # In the connection, you can assign the PDO to a static
                # variable to send it back if it's already set
                if(self::$con instanceof \PDO)
                    return self::$con;
                # If not already a PDO connection, try and make one
                try {
                        # PDO settings you can apply at connection time
                        $opts = array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,PDO::ATTR_EMULATE_PREPARES => false);
                        # Assign your PDO Conneciton here.
                        self::$con =  new PDO("mysql:host={$host};dbname={$database}",$username,$password,$opts);
                        # Return the connection
                        return self::$con;
                    }
                catch (PDOException $e){
                        exit('Database error');
                    }   
            }
    }

您可以在函数内外的任何地方使用它，类，随您便。每次都会 return 相同的连接。如果您将 spl_autoload_register() 与自动加载功能一起使用，您将万事俱备，甚至不必每次都显式使用 require_once()！

<?php
require_once('class.DatabaseConnection.php');
// Instantiate connection class
$pdo = new DatabaseConnection();
// Assign the connection to $con (or whatever variable you like)
$con = $pdo->connection();

请注意，singleton 模式通常很少使用。通常使用 new Objects() 而不分配 singleton 会更好。不过，我个人喜欢 singleton 用于此用途。

简单演示 - 考虑这种情况：

<?php
// Here is an example of the singlton with an echo
// which shows that the class is returning itself
// like a global
class DatabaseConnection
    {
        private static $singleton;
        public function __construct()
           {
                // If your singleton is not set
                if(!isset(self::$singleton)) {
                        echo 'NEW Object'.PHP_EOL;
                        // assign it this class
                        self::$singleton = $this;
                    }
                else
                    echo 'SAME Object'.PHP_EOL;
                // return this class
                return self::$singleton;
           }
    }

function ReturnConnection()
    {
        return new DatabaseConnection();
    }

class TestClass
    {
        public  function __construct()
            {
                new DatabaseConnection();
            }
    }

function query($sql=false)
    {
        return ReturnConnection();
    }

// The connection class wrapped in a function 
$a = ReturnConnection();
// The function nested inside a class
$b = new TestClass();
// The function nested inside another function
$c = query();

上述 singleton 的使用将产生：

NEW Object
SAME Object
SAME Object

PHP Class - 如何只连接一次数据库

PHP Class - How to connect to the database only once

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