这个问题主要提示是，不能通过'/tmp/mysql.sock'连到服务器，而php标准配置正是用过'/tmp/mysql.sock'，但是一些mysql安装方法将mysql.sock放在/var/lib/mysql.sock或者其他的什么地方，你可以通过修改/etc/my.cnf文件来修正它，打开文件，可以看到如下的东东：
[mysqld]
socket=/var/lib/mysql.sock
改一下就好了，但也会引起其他的问题，如mysql程序连不上了，再加一点：
[mysql]
socket=/tmp/mysql.sock
或者还可以通过修改php.ini中的配置来使php用其他的mysql.sock来连，这个大家自己去找找

或者用这样的方法:
ln -s /var/lib/mysql/mysql.sock /tmp/mysql.sock

还有:
phpmyadmin的说明书有说
The error message "Warning: MySQL Connection Failed: Can't connect to local MySQL server through socket '/tmp/mysql.sock' (111)..." is displayed. What can I do?

For RedHat users, Harald Legner suggests this on the mailing list:

On my RedHat-Box the socket of mysql is /var/lib/mysql/mysql.sock. In your php.ini you will find a line
mysql.default_socket = /tmp/mysql.sock
change it to
mysql.default_socket = /var/lib/mysql/mysql.sock
Then restart apache and it will work.

Here is a fix suggested by Brad Ummer in the phpwizard forum:

First, you need to determine what socket is being used by MySQL.
To do this, telnet to your server and go to the MySQL bin directory. In this directory there should be a file named mysqladmin. Type ./mysqladmin variables, and this should give you a bunch of info about your MySQL server, including the socket (/tmp/mysql.sock, for example).
Then, you need to tell PHP to use this socket.
Assuming you are using PHP 3.0.10 or better, you can specify the socket to use when you open the connection. To do this in phpMyAdmin, you need to complete the socket information in the config.inc.php3.
For example: $cfg['Servers'][$i]['socket'] = '/tmp/mysql.sock';