PHP code example to implement Mysql read-write separation

<?php
/****************************
*** mysql-rw-php version 0.1
*** code by hqlulu#gmail.com
*** http://bbs.it-home.org
*** 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();
}
}
?>