How to achieve separation of reading and writing in PHP

There are several ways to separate reading and writing in MySQL

1. MySQL middleware

2. MySQL Driver layer

3. Code control

I won’t go into details about the middleware and driver layer here. Let’s briefly introduce how to control it through PHP code. MySQL reads and writes separated.

We all know that "reading" in the SQL statement is "SELECT" and "writing" is "INSERT", so the first thing we should think of is the string interception substr() function.

First we use the substr() function to get whether the first 6 characters of the sql statement are "SELECT". If so, we connect to the read server for processing. If not, we connect to the write server for processing.

Example code:

$querystr = strtolower(trim(substr($sql,0,6)));    //截取SQL语句字符串

//如果是select，就连接slave(从)服务器
if($querystr == 'select')
{
　　$slave_server='192.168.80.3::3306';
　　$dsn="mysql:host=$slave_server;dbname=3d";
　　$user='root';
　　$pass='root';
　　$dbh=new PDO($dsn, $user, $pass);
　　$res=$dbh->query($sql)->fetchAll(PDO::FETCH_ASSOC);
}
//如果不是select，就连接master(主)服务器
else
{
　　$master_server='192.168.33.22::3306';
　　$dsn="mysql:host=$master_server;dbname=3dprintsys";
　　$user='root';
　　$pass='123456';
　　$dbh=new PDO($dsn, $user, $pass);
　　$res=$dbh->exec($sql);
}

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