1、Introduction
之前写过2篇文章，分别是：
Mysql主从同步的原理
Myql主从同步实战
基于此，我们再实现简单的PHP+Mysql读写分离，从而提高数据库的负载能力。
2、代码实战
<?php
class Db
{
private $res;
function __construct($sql)
{
$querystr = strtolower(trim(substr($sql,0,6)));
//如果是select，就连接slave服务器
if($querystr == 'select')
{
$res=$this->slave_select($sql);
$this->res=$res;
}
//如果不是select，就连接master服务器
else
{
$res=$this->master_change($sql);
$this->res=$res;
}
}
/**
* slave从库返回sql查询结果
* @param $sql
* @return array
*/
private function slave_select($sql){
//该处只是随机获取slave节点的ip，当然，还可以采用其他算法获取slave_ip
$slave_server=$this->get_slave_ip();
$dsn="mysql:host=$slave_server;dbname=test";
$user='root';
$pass='123456';
$dbh=new PDO($dsn, $user, $pass);
return $dbh->query($sql)->fetchAll(PDO::FETCH_ASSOC);
}
/**master主库返回sql执行结果
* @param $sql
* @return int
*/
private function master_change($sql){
$master_server='192.168.33.22';
$dsn="mysql:host=$master_server;dbname=test";
$user='root';
$pass='123456';
$dbh=new PDO($dsn, $user, $pass);
return $dbh->exec($sql);
}
/**
* 随机获取slave-ip
* @return mixed
*/
private function get_slave_ip(){
$slave_ips=['192.168.33.33','192.168.33.44'];
$count=count($slave_ips)-1;
$random_key=mt_rand(0,$count);
return $slave_ips[$random_key];
}
/**
* 获取结果
* @return int
*/
public function get_res(){
return $this->res;
}
}
$sql1 = "select * from t1";
$sql2 = "insert into t1 (name) values ('haha')";
$sql3 = "delete from t1 where id=1";
$sql4 = "update t1 set name='Jerry' where id=2";
$db = new Db($sql1);
//$db = new Db($sql2);
//$db = new Db($sql3);
//$db = new Db($sql4);
var_dump($db->get_res());