mysqli不能使用localhost，請問這是怎麼回事？

代碼如下：

connect_error) {    die('Connect Error (' . $mysqli->connect_errno . ') '            . $mysqli->connect_error);};echo 'ok';

• 如果上面串連地址為'localhost'就會報錯，如下：

  Warning: mysqli::mysqli(): (HY000/2002): No such file or directory in /mnt/www/cglevi/publichtml/mysql.php on line 2Connect Error (2002) No such file or directory

• 將'localhost'修改為'127.0.0.1'之後連結正常

查看了hosts沒有問題，如下：

127.0.0.1 localhost::1         localhost localhost.localdomain localhost6 localhost6.localdomain6/etc/hosts (END) 

查看mysql狀態，沒有問題，如下：

mysql> status;--------------mysql  Ver 14.14 Distrib 5.6.10, for Linux (x86_64) using  EditLine wrapperConnection id:      860Current database:   Current user:       root@localhostSSL:            Not in useCurrent pager:      stdoutUsing outfile:      ''Using delimiter:    ;Server version:     5.6.10 MySQL Community Server (GPL)Protocol version:   10Connection:     Localhost via UNIX socketServer characterset:    latin1Db     characterset:    latin1Client characterset:    utf8Conn.  characterset:    utf8UNIX socket:        /var/lib/mysql/mysql.sockUptime:         13 hours 13 min 50 secThreads: 1  Questions: 11900  Slow queries: 0  Opens: 100  Flush tables: 1  Open tables: 80  Queries per second avg: 0.249--------------

請問如何解決？

回複內容：

代碼如下：

connect_error) {    die('Connect Error (' . $mysqli->connect_errno . ') '            . $mysqli->connect_error);};echo 'ok';

• 如果上面串連地址為'localhost'就會報錯，如下：

  Warning: mysqli::mysqli(): (HY000/2002): No such file or directory in /mnt/www/cglevi/publichtml/mysql.php on line 2Connect Error (2002) No such file or directory

• 將'localhost'修改為'127.0.0.1'之後連結正常

查看了hosts沒有問題，如下：

127.0.0.1 localhost::1         localhost localhost.localdomain localhost6 localhost6.localdomain6/etc/hosts (END) 

查看mysql狀態，沒有問題，如下：

mysql> status;--------------mysql  Ver 14.14 Distrib 5.6.10, for Linux (x86_64) using  EditLine wrapperConnection id:      860Current database:   Current user:       root@localhostSSL:            Not in useCurrent pager:      stdoutUsing outfile:      ''Using delimiter:    ;Server version:     5.6.10 MySQL Community Server (GPL)Protocol version:   10Connection:     Localhost via UNIX socketServer characterset:    latin1Db     characterset:    latin1Client characterset:    utf8Conn.  characterset:    utf8UNIX socket:        /var/lib/mysql/mysql.sockUptime:         13 hours 13 min 50 secThreads: 1  Questions: 11900  Slow queries: 0  Opens: 100  Flush tables: 1  Open tables: 80  Queries per second avg: 0.249--------------

請問如何解決？

開始的回答有點不嚴謹，估計也沒有解決問題，修改了答案：

問題出現的原因：

當主機填寫為localhost時MySQL會採用 unix domain socket串連，當主機填寫為127.0.0.1時MySQL會採用TCP/IP的方式串連。使用Unix socket的串連比TCP/IP的串連更加快速與安全。這是MySQL串連的特性，可以參考官方文檔的說明4.2.2. Connecting to the MySQL Server：

On Unix, MySQL programs treat the host name localhost specially, in a way that is likely different from what you expect compared to other network-based programs. For connections to localhost, MySQL programs attempt to connect to the local server by using a Unix socket file. This occurs even if a --port or -P option is given to specify a port number. To ensure that the client makes a TCP/IP connection to the local server, use --host or -h to specify a host name value of 127.0.0.1, or the IP address or name of the local server. You can also specify the connection protocol explicitly, even for localhost, by using the --protocol=TCP option.

這個問題有以下幾種解決方案：

1. 使用TCP/IP代替Unix socket。即在串連的時候將localhost換成127.0.0.1。

2. 修改MySQL的設定檔my.cnf，指定mysql.socket的位置：

   /var/lib/mysql/mysql.sock (你的mysql.socket路徑)。

3. 直接在php建立串連的時候指定my.socket的位置（官方文檔：mysqli_connect）。比如：

   $db = new MySQLi('localhost', 'root', 'root', 'my_db', '3306', '/var/run/mysqld/mysqld.sock')

如果哪裡沒有說清楚或者說錯了，歡迎提出了～～

參考這個問題： http://segmentfault.com/q/1010000000320989

提問之前記得先搜尋。

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