php 不能连接数据库 php error Can't connect to local MySQL server through socket '/tmp/mysql.sock'

测试的php文件

<?php

$link=mysql_connect('localhost','root','zz') or die(mysql_error());

mysql_select_db('test') or die('no db');

mysql_query('SET NAMES utf8');
echo 99;
?>

运行后报错

 Can't connect to local MySQL server through socket '/tmp/mysql.sock'

但在 命令行中能进入mysql

[root@localhost local]# mysql -u root -p

Enter password: 

Welcome to the MySQL monitor.  Commands end with ; or \g.Your MySQL connection id is 3Server version: 5.5.2-m2 Source distribution
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> 

解决办法

chown -R root /usr/local/mysql 
chgrp -R mysql /usr/local/mysql 
chown -R root /usr/local/mysql/bin 
chgrp -R mysql /usr/local/mysql/bin 
chgrp -R mysql /var/lib/mysql 
chmod 777 /var/lib/mysql 
chown -R root /var/lib/mysql/mysql 
chgrp -R mysql /var/lib/mysql/mysql 
chmod 777 /var/lib/mysql/mysql 
chown -R root /var/lib/mysql/mysql/* 
chgrp -R mysql /var/lib/mysql/mysql/* 
chmod 777 /var/lib/mysql/mysql/* 
chmod 777 /usr/local/mysql/lib/mysql/libmysqlclient.a