解析PHP實現的Mysql讀寫分離_PHP教程

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PHP實現的Mysql讀寫分離

主要特性：

1 簡單的讀寫分離
2 一個主數據庫，可以添加更多的只讀數據庫
3 讀寫分離但不用擔心某些特性不支持
4 缺點：同時連接兩個數據庫

英文比較爛，也寫幾個字吧

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代碼：

mysql_rw_php.class.php

<?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 {

 //查詢個數
 var $querynum = 0;
 //當前操作的數據庫連接
 var $link = null;
 //字符集
 var $charset;
 //當前數據庫
 var $cur_db = '';

 //是否存在有效的只讀數據庫連接
 var $ro_exist = false;
 //只讀數據庫連接
 var $link_ro = null;
 //讀寫數據庫連接
 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');
 }
 }

 //只讀連接失敗
 if(!$this->link && !$halt) return false;

 //未初始化rw時，第一個連接作為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);
 }
 }

 //連接一個只讀的mysql數據庫
 function connect_ro($dbhost, $dbuser, $dbpw, $dbname = '', $pconnect = 0){
 if($this->link_rw == null)
 $this->link_rw = $this->link;
 $this->link = null;
 //不產生halt錯誤
 $this->connect($dbhost, $dbuser, $dbpw, $dbname, $pconnect, false);
 if($this->link){
 //連接成功
 //echo "link ro sussess! ";
 $this->ro_exist = true;
 $this->link_ro = $this->link;
 if($this->cur_db){
 //如果已經選擇過數據庫則需要操作一次
 @mysql_select_db($this->cur_db, $this->link_ro);
 }
 }else{
 //連接失敗
 //echo "link ro failed! ";
 $this->link = &$this->link_rw;
 }
 }

 //設置一系列只讀數據庫并且連接其中一個
 function set_ro_list($ro_list){
 if(is_array($ro_list)){
 //隨機選擇其中一個
 $link_ro = $ro_list[array_rand($ro_list)];
 $this->connect_ro($link_ro['dbhost'], $link_ro['dbuser'], $link_ro['dbpw']);
 }
 }

 function select_db($dbname) {
 //同時操作兩個數據庫連接
 $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;
 //判斷是否select語句
 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;\">
 MySQL Error 
 Message: $message 
 SQL: $sql 
 Error: $dberror 
 Errno.: $dberrno 
 </div>";
 exit();
 }
}

?>

example.php