本代码是从uchome的代码修改的，是因为要解决uchome的效率而处理的。

这个思维其实很久就有了，只是一直没有去做，相信也有人有同样的想法，如果有类似的，那真的希望提出相关的建议。

封装的方式比较简单，增加了只读数据库连接的接口扩展，不使用只读数据库也不影响原代码使用。

有待以后不断完善。。

希望给有需要的朋友带来帮助。

PHP实现的Mysql读写分离

主要特性：

简单的读写分离

一个主数据库，可以添加更多的只读数据库

读写分离但不用担心某些特性不支持

缺点：同时连接两个数据库

英文比较烂，也写几个字吧

php code for mysql read/write split

feature:

simply rw split

one master,can add more slaves

support all mysql feature

link to the master and slave at the same time

PHP代码：

mysql_rw_php.class.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!
";

$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!
";

$this->link = &$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 "

";

exit();

}

}

?>

example.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];

}

?>

转自http://www.blueidea.com/tech/program/2009/6636.asp