解析PHP实现的Mysql读写分离

<?php

/****************************************
*** mysql-rw-php version 0.1 @ 2009-4-16
*** code by hqlulu#gmail.com
*** http://www.aslibra.com
*** http://code.google.com/p/mysql-rw-php/
*** code modify from class_mysql.php (uchome)
****************************************/

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 = '';

   //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 = '', $pconnect = 0, $halt = TRUE) {
     if($pconnect) {
       if(!$this->link = @mysql_pconnect($dbhost, $dbuser, $dbpw)) {
         $halt && $this->halt('Can not connect to MySQL server');
       }
     } else {
       if(!$this->link = @mysql_connect($dbhost, $dbuser, $dbpw)) {
         $halt && $this->halt('Can not connect to MySQL server');
       }
     }
    
     //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($this->version() > '4.1') {
       if($this->charset) {
         @mysql_query("SET character_set_connection=$this->charset, character_set_results=$this->charset, character_set_client=binary", $this->link);
       }
       if($this->version() > '5.0.1') {
         @mysql_query("SET sql_mode=''", $this->link);
       }
     }
     if($dbname) {
       $this->select_db($dbname);
     }
   }

   //连接一个只读的mysql数据库
   function connect_ro($dbhost, $dbuser, $dbpw, $dbname = '', $pconnect = 0){
     if($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['dbhost'], $link_ro['dbuser'], $link_ro['dbpw']);
     }
   }

   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 = '') {
     $qr = $this->query($sql, $type);
     return $this->fetch_array($qr);
   }

   function query($sql, $type = '') {
     $this->link = &$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 = $type == 'UNBUFFERED' && @function_exists('mysql_unbuffered_query') ?
       'mysql_unbuffered_query' : 'mysql_query';
     if(!($query = $func($sql, $this->link)) && $type != 'SILENT') {
       $this->halt('MySQL Query Error', $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 = '', $sql = '') {
     $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

/****************************************
*** mysql-rw-php version 0.1 @ 2009-4-16
*** code by hqlulu#gmail.com
*** http://www.aslibra.com
*** http://code.google.com/p/mysql-rw-php/
*** code modify from class_mysql.php (uchome)
****************************************/

require_once('mysql_rw_php.class.php');

//rw info
$db_rw = array(
   'dbhost'=>'www.aslibra.com',
   'dbuser'=>'aslibra',
   'dbpw'=>'www.aslibra.com',
   'dbname'=>'test'
);

$db_ro = array(
   array(
     'dbhost'=>'www.aslibra.com:4306',
     'dbuser'=>'aslibra',
     'dbpw'=>'www.aslibra.com'
   )
);

$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='test'";
$DB->query($sql);

//send to ro
$sql = "select * from a";
$qr = $DB->query($sql);
while($row = $DB->fetch_array($qr)){
   echo $row[a];
}
?>