PHP设计模式之适配器模式

1.说明

1.适配器模式： 能够将截然不同的函数接口封装成统一的API
2.实际应用举例，PHP的数据库操作有mysql, mysqli, pdo3种。能够用适配器模式统一成一致。相似的场景还有cache适配器，就是将memcache，redis，file，apc等不同的缓存函数统一成一致的
3.以下的样例能够帮助你对付各种数据库链接功能，mysql mysqli, pdo随便选，操作都抽象为统一的接口client不须要改动一行数据库链接方式

2.创建一个接口

interface IDatabase
{
    function connect($host, $user, $passwd, $dbname);
    function query($sql);
    function close();
}

3.Mysql封装

class MySQL implements IDatabase
{
    protected $conn;
    function connect($host, $user, $passwd, $dbname)
    {
        $conn = mysql_connect($host, $user, $passwd);
        mysql_select_db($dbname, $conn);
        $this->conn = $conn;
    }

    function query($sql)
    {
        $res = mysql_query($sql, $this->conn);
        return $res;
    }

    function close()
    {
        mysql_close($this->conn);
    }
}

4.MySqli封装

class MySQLi implements IDatabase
{
    protected $conn;

    function connect($host, $user, $passwd, $dbname)
    {
        $conn = mysqli_connect($host, $user, $passwd, $dbname);
        $this->conn = $conn;
    }

    function query($sql)
    {
        return mysqli_query($this->conn, $sql);
    }

    function close()
    {
        mysqli_close($this->conn);
    }
}

5.PDO封装

class PDO implements IDatabase
{
    protected $conn;
    function connect($host, $user, $passwd, $dbname)
    {
        $conn = new \PDO("mysql:host=$host;dbname=$dbname", $user, $passwd);
        $this->conn = $conn;
    }

    function query($sql)
    {
        return $this->conn->query($sql);
    }

    function close()
    {
        unset($this->conn);
    }
}

6.实例调用，（统一接口调用）

$db = new PDO();
$db->connect('127.0.0.1', 'root', 'root', 'test');
$db->query('show databases');
$db->close();

$db = MySQLi ();
$db->connect('127.0.0.1', 'root', 'root', 'test');
$db->query('show databases');
$db->close();

$db = MySQl PDO();
$db->connect('127.0.0.1', 'root', 'root', 'test');
$db->query('show databases');
$db->close();