php連不上mysql: mysqli::__construct(): (HY000/2002): No such file or directory in..

<?php
$USER ='root';
$PW   ='pwpwpw';
$HOST ='localhost';

$mysqli = new mysqli($HOST, $USER, $PW, 'test');
if ($mysqli->connect_error) {
        echo $mysqli->connect_errno;
        echo "\n";
        echo $mysqli->connect_error;
        echo "\n";
} else {
  echo "ok";
}

執行後出現：
     PHP Warning:  mysqli::__construct(): (HY000/2002): No such file or directory in /home/web/mysql_test.php on line 6


查一下 mysql status

mysql> status
--------------
mysql  Ver 8.0.22-0ubuntu0.20.04.3 for Linux on x86_64 ((Ubuntu))

Connection id:          4
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.7.33-log Source distribution
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    utf8
Db     characterset:    utf8
Client characterset:    utf8
Conn.  characterset:    utf8
UNIX socket:            /tmp/mysqld.sock
Binary data as:         Hexadecimal
Uptime:                 46 sec

Threads: 1  Questions: 8  Slow queries: 0  Opens: 110  Flush tables: 1  Open tables: 32  Queries per second avg: 0.173
--------------

簡單解決 方法1

修改 php 中的 mysql 連接方式
加上 /tmp/mysql.sock

$mysqli = new mysqli($HOST, $USER, $PW, 'test', null , '/tmp/mysql.sock');

 

 

簡單解決 方法2

修改 php.ini

pdo_mysql.default_socket=/tmp/mysql.sock
mysql.default_socket=/tmp/mysql.sock
mysqli.default_socket=/tmp/mysql.sock

(要重啟 apache httpd 或 nginx)

 

最簡單的解決 方法3

 ln -s /tmp/mysql.sock /var/lib/mysql/mysql.sock

 
 
 查看  phpinfo() 資料
看一下 default_socket 的路徑
問題出在 php內的 socket 路徑跟 mysql server 的 /tmp/mysqld.sock 不同



只要修改 my.ini
將 socket 改為：

[client]
socket          =  /var/run/mysqld/mysqld.sock

[mysqld]
socket          =  /var/run/mysqld/mysqld.sock

重啟 mysqld 即可