php如何连接主从数据库

<?php

class mysql_rw_php {
  //查询个数
  var $querynum = 0;
  //当前操作的数据库连接
  var $link = null;
  //字符集
  var $charset;
  //当前数据库
  var $cur_db = &#39;&#39;;
  //是否存在有效的只读数据库连接
  var $ro_exist = false;
  //只读数据库连接
  var $link_ro = null;
  //读写数据库连接
  var $link_rw = null;
  function mysql_rw_php(){
  }
  function connect($dbhost, $dbuser, $dbpw, $dbname = &#39;&#39;, $pconnect = 0, $halt = TRUE) {
    if($pconnect) {
      if(!$this->link = @mysql_pconnect($dbhost, $dbuser, $dbpw)) {
        $halt && $this->halt(&#39;Can not connect to MySQL server&#39;);
      }
    } else {
      if(!$this->link = @mysql_connect($dbhost, $dbuser, $dbpw)) {
        $halt && $this->halt(&#39;Can not connect to MySQL server&#39;);
      }
    }
    
    //只读连接失败
    if(!$this->link && !$halt) return false;
    
    //未初始化rw时，第一个连接作为rw
    if($this->link_rw == null)
      $this->link_rw = $this->link;
    if($this->version() > &#39;4.1&#39;) {
      if($this->charset) {
        @mysql_query("SET character_set_connection=$this->charset, character_set_results=$this->charset, character_set_client=binary", $this->link);
      }
      if($this->version() > &#39;5.0.1&#39;) {
        @mysql_query("SET sql_mode=&#39;&#39;", $this->link);
      }
    }
    if($dbname) {
      $this->select_db($dbname);
    }
  }
  //连接一个只读的mysql数据库
  function connect_ro($dbhost, $dbuser, $dbpw, $dbname = &#39;&#39;, $pconnect = 0){
    if($this->link_rw == null)
      $this->link_rw = $this->link;
    $this->link = null;
    //不产生halt错误
    $this->connect($dbhost, $dbuser, $dbpw, $dbname, $pconnect, false);
    if($this->link){
      //连接成功
      //echo "link ro sussess!<br>";
      $this->ro_exist = true;
      $this->link_ro = $this->link;
      if($this->cur_db){
        //如果已经选择过数据库则需要操作一次
        @mysql_select_db($this->cur_db, $this->link_ro);
      }
    }else{
      //连接失败
      //echo "link ro failed!<br>";
      $this->link = &$this->link_rw;
    }
  }
  //设置一系列只读数据库并且连接其中一个
  function set_ro_list($ro_list){
    if(is_array($ro_list)){
      //随机选择其中一个
      $link_ro = $ro_list[array_rand($ro_list)];
      $this->connect_ro($link_ro[&#39;dbhost&#39;], $link_ro[&#39;dbuser&#39;], $link_ro[&#39;dbpw&#39;]);
    }
  }
  function select_db($dbname) {
    //同时操作两个数据库连接
    $this->cur_db = $dbname;
    if($this->ro_exist){
      @mysql_select_db($dbname, $this->link_ro);
    }
    return @mysql_select_db($dbname, $this->link_rw);
  }
  function fetch_array($query, $result_type = MYSQL_ASSOC) {
    return mysql_fetch_array($query, $result_type);
  }
  function fetch_one_array($sql, $type = &#39;&#39;) {
    $qr = $this->query($sql, $type);
    return $this->fetch_array($qr);
  }
  function query($sql, $type = &#39;&#39;) {
    $this->link = &$this->link_rw;
    //判断是否select语句
    if($this->ro_exist && preg_match ("/^(\s*)select/i", $sql)){
      $this->link = &$this->link_ro;
    }
    $func = $type == &#39;UNBUFFERED&#39; && @function_exists(&#39;mysql_unbuffered_query&#39;) ?
      &#39;mysql_unbuffered_query&#39; : &#39;mysql_query&#39;;
    if(!($query = $func($sql, $this->link)) && $type != &#39;SILENT&#39;) {
      $this->halt(&#39;MySQL Query Error&#39;, $sql);
    }
    $this->querynum++;
    return $query;
  }
  function affected_rows() {
    return mysql_affected_rows($this->link);
  }
  function error() {
    return (($this->link) ? mysql_error($this->link) : mysql_error());
  }
  function errno() {
    return intval(($this->link) ? mysql_errno($this->link) : mysql_errno());
  }
  function result($query, $row) {
    $query = @mysql_result($query, $row);
    return $query;
  }
  function num_rows($query) {
    $query = mysql_num_rows($query);
    return $query;
  }
  function num_fields($query) {
    return mysql_num_fields($query);
  }
  function free_result($query) {
    return mysql_free_result($query);
  }
  function insert_id() {
    return ($id = mysql_insert_id($this->link)) >= 0 ? $id : $this->result($this->query("SELECT last_insert_id()"), 0);
  }
  function fetch_row($query) {
    $query = mysql_fetch_row($query);
    return $query;
  }
  function fetch_fields($query) {
    return mysql_fetch_field($query);
  }
  function version() {
    return mysql_get_server_info($this->link);
  }
  function close() {
    return mysql_close($this->link);
  }
  function halt($message = &#39;&#39;, $sql = &#39;&#39;) {
    $dberror = $this->error();
    $dberrno = $this->errno();
    echo "<div style=\"position:absolute;font-size:11px;font-family:verdana,arial;background:#EBEBEB;padding:0.5em;\">
        <b>MySQL Error</b><br>
        <b>Message</b>: $message<br>
        <b>SQL</b>: $sql<br>
        <b>Error</b>: $dberror<br>
        <b>Errno.</b>: $dberrno<br>
        </div>";
    exit();
  }
}
?>

<?php

require_once(&#39;mysql_rw_php.class.php&#39;);
//rw info
$db_rw = array(
  &#39;dbhost&#39;=>&#39;www.aslibra.com&#39;,
  &#39;dbuser&#39;=>&#39;aslibra&#39;,
  &#39;dbpw&#39;=>&#39;www.aslibra.com&#39;,
  &#39;dbname&#39;=>&#39;test&#39;
);
$db_ro = array(
  array(
    &#39;dbhost&#39;=>&#39;www.aslibra.com:4306&#39;,
    &#39;dbuser&#39;=>&#39;aslibra&#39;,
    &#39;dbpw&#39;=>&#39;www.aslibra.com&#39;
  )
);
$DB = new mysql_rw_php;
//connect Master
$DB->connect($db_rw[dbhost], $db_rw[dbuser], $db_rw[dbpw], $db_rw[dbname]);
//Method 1: connect one server
$DB->connect_ro($db_ro[0][dbhost], $db_ro[0][dbuser], $db_ro[0][dbpw]);
//Method 2: connect one server from a list by rand
$DB->set_ro_list($db_ro);
//send to rw
$sql = "insert into a set a=&#39;test&#39;";
$DB->query($sql);
//send to ro
$sql = "select * from a";
$qr = $DB->query($sql);
while($row = $DB->fetch_array($qr)){
  echo $row[a];
}
?>