PHP로 구현된 mysql 읽기-쓰기 분리 관련 내용

<?php
/**
* mysql读写分离
*/
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)==&#39;select&#39;)
    {
      echo &#39;I am using slave db..<br>&#39;;
      $link = mysql_connect("192.168.20.201:3306", "open", "123456") or die("Could not connect: " . mysql_error());
      mysql_select_db("hadoop");
      $result = mysql_query($sql);
      while($row = mysql_fetch_array($result,MYSQL_ASSOC)){
        $data[]=$row;
      }
      //print_r($data);exit;
      echo mysql_get_host_info($link).mysql_get_server_info($link).mysql_get_proto_info($link).mysql_get_client_info().&#39;<br>&#39;;
    }else{
      echo &#39;I am using master db..<br>&#39;;
      $link = mysql_connect("192.168.20.195:3306","open","123456") or die("Could not connect: " . mysql_error());
      mysql_select_db("hadoop");
      $result = mysql_query($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().&#39;<br>&#39;;
    }
  }
}
$master = new db("INSERT INTO user (id,name)VALUES (NULL,&#39;100&#39;)");
$slave = new db("SELECT * from `user`");