php无法使用localhost连接mysql服务器
在redhat下安装了mysql，在mysql控制台下，可以使用localhost连接，但是在php中连接时，却不行，而使用127.0.0.1能连上，查看了hosts文件，发现有127.0.0.1和localhost的对应

哪位大侠知道是怎么回事

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是不是你在建站点的时候设置了站点为http://127.0.0.1了呢？
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看一看你的mysql是怎么配置的，
检查mysql启动后/usr/local/mysql/var/mysql.sock是否存在。
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Description
A frequent error message received when using the mysql command line utility is: Can 't connect to local MySQL server through socket '/tmp/mysql.sock ' While this error message can be frustrating, the solution is simple.

Directions
When connecting to a MySQL server located on the local system, the mysql client connects thorugh a local file called a socket instead of connecting to the localhost loopback address 127.0.0.1. For the mysql client, the default location of this socket file is /tmp/mysql.sock. However, for a variety of reasons, many MySQL installations place this socket file somewhere else like /var/lib/mysql/mysql.sock.

While it is possible to make this work by specifying the socket file directly in the mysql client command

mysql --socket=/var/lib/mysql/mysql.sock ...


it is painful to type this in every time. If you must do so this way (because you don 't have permissions to the file in the solution below), you could create an alias in your shell to make this work

(like alias mysql= "mysql --socket=/var/lib/mysql/mysql.sock " depending on your shell).

To make your life easier, you can make a simple change to the MySQL configuration file /etc/my.cnf that will permanently set the socket file used by the mysql client. After making a backup copy of /etc/my.cnf, open it in your favorite editor. The file is divided into sections such as

[mysqld]
datadir=/usr/local/mysql/data
socket=/var/lib/mysql/mysql.sock

[mysql.server]
user=mysql
basedir=/usr/local/mysql

If there is not currently a section called [client], add one at the bottom of the file and copy the socket= line under the [mysqld] section such as:

[client]
socket=/var/lib/mysql/mysql.sock

If there is already a [client] section in the my.cnf file, add or edit the socket line as appropriate. You won 't need to restart your server or any other processes. Subsequent uses of the mysql client will use the proper socket file.