PHP无法连接数据库的解决办法总结：
1、获取当前 mysql.default_socket、mysqli.default_socket、pdo_mysql.default_socket 配置信息
建立一个 PHP 文件，显示 phpinfo()，用浏览器打开如图:
在此页面，找到mysql.default_socket、mysqli.default_socket、pdo_mysql.default_socket信息
2、获取 MySQL socket 路径
通过控制台进入 MySQL, 输入命令: STATUS, 查找 UNIX socket 值
#mysql -u root -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 8 Server version: 5.7.11 MySQL Community Server (GPL) Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement. mysql> STATUS -------------- mysql Ver 14.14 Distrib 5.7.11, for osx10.9 (x86_64) using EditLine wrapper Connection id: 8 Current database: Current user: root@localhost SSL: Not in use Current pager: less Using outfile: ‘‘ Using delimiter: ; Server version: 5.7.11 MySQL Community Server (GPL) Protocol version: 10 Connection: Localhost via UNIX socket Server characterset: utf8 Db characterset: utf8 Client characterset: utf8 Conn. characterset: utf8 UNIX socket: /tmp/mysql.sock Uptime: 8 days 15 hours 1 min 17 sec Threads: 2 Questions: 21 Slow queries: 0 Opens: 114 Flush tables: 1 Open tables: 0 Queries per second avg: 0.000 --------------
3、这时候, 你对比 mysql.default_socket、mysqli.default_socket、pdo_mysql.default_socket 和 通过 MySQL UNIX socket 发现不一样, 这就是 mysql_connect(); 警告的原因: PHP 配置 mysql 有问题。
4、重新配置 PHP, 打开php.ini修改mysql.default_socket、mysqli.default_socket、pdo_mysql.default_socket 的值为: /tmp/mysql.sock
pdo_mysql.default_socket=/tmp/mysql.sock mysql.default_socket=/tmp/mysql.sock mysqli.default_socket=/tmp/mysql.sock
或者修改my.cnf的socket：
[client] socket=/tmp/mysql.sock [mysqld] socket=/tmp/mysql.sock
5、重启nginx或者apache
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