适配器模式（数据库方面）支持不同的数据库连接

<?php

define("BASDIR",__DIR__);
include  BASDIR."/Phpclass/Loader.php";
spl_autoload_register("\\Phpclass\\Loader::autoload_rege");


$mysqli= new \Phpclass\Databases\Mysqlis();

$mysqli->connect("localhost","root","root","nfyx");

$sql="select name from test where id>0";
$res=$mysqli->query($sql);


foreach ($res as $row)
{
    echo $row['name']."\n";
}

$mysqli->close();

$mysqli= new \Phpclass\Databases\PDOS();

$mysqli->connect("localhost","root","root","nfyx");

$sql="select name from test where id>0";
foreach ($mysqli->query($sql,PDO::FETCH_ASSOC) as $row)
    {
        print_r($row);
    }

$mysqli->close();
-------------------------------------------------------------------Index2.php

<?php

namespace Phpclass\Databases;
use mysqli;

class Mysqlis implements \Phpclass\IDatabase
{
    static protected $conn;
    function connect($host, $user, $passwd, $db)
    {
        self::$conn = new mysqli($host,$user,$passwd,$db);

        if (self::$conn->connect_errno)
        {
            die("连接数据库失败".self::$conn->connect_error);
        }
    }

    function query($sql)
    {
        return self::$conn->query($sql);
    }
    function close()
    {
       self::$conn=null;
    }

}

-------------------------------------------------------------------Mysqlis.php

<?php
namespace Phpclass\Databases;
use PDO;

class PDOS implements \Phpclass\IDatabase
{
    static protected $conn;
    function connect($host, $user, $passwd, $db)
    {
        try {

        self::$conn = new PDO("mysql:host=$host;dbname=$db", $user, $passwd);

        } catch (PDOException $e) {
            echo 'Connection failed: ' . $e->getMessage();
        }
    }

    function query($sql)
    {
        return self::$conn->query($sql);
    }
    function close()
    {
        self::$conn=null;
    }

}

-------------------------------------------------------------------PDOS.php