PHP 数据库读写分离的经典例子

<?
/**
* mysql读写分离
* edit: www.jb200.com
*/
class db
{
    public function __construct($sql)
    {
        $chestr = strtolower(trim($sql));
        //判断sql语句有select关键字的话，就连接读的数据库,否则就连接写数据库
        if(substr($chestr,0,6)=='select')
        {
            echo 'I am using select db..<br>';
            $link = mysql_connect("127.0.0.1:3306", "root", "") or die("Could not connect: " . mysql_error());
            mysql_select_db("test");
            $result = mysql_query($sql);
            while ($row = mysql_fetch_array($result, MYSQL_NUM))
            {
                printf("%s %s", $row[0],$row[1]);
            }
            echo mysql_get_host_info($link).mysql_get_server_info($link).mysql_get_proto_info($link).mysql_get_client_info().'<br>';        
        }
        else
        {
            echo 'I am using insert db..<br>';
            $link = mysql_connect("127.0.0.2:3306","root","") or die("Could not connect: " . mysql_error());
            mysql_select_db("test");
            $result = mysql_query($sql);
            echo @mysql_affected_rows($result);
            echo mysql_get_host_info($link).mysql_get_server_info($link).mysql_get_proto_info($link).mysql_get_client_info().'<br>';       
        }
         
    }
}
 
$d = new db("  update `users` set `select`='fasdf' where `id` =1");
$d2 = new db("         SELECT * from `users`");