我协助查看了下，确实如此，无论是指定IP、端口的tcp/ip方式连接，或者是用unix socket方式连接，报错信息都类似：
代码如下:
Could not connect: Can't connect to MySQL server on 'MYSQL.SERVER' (13)
而如果用命令行人工连接MySQL，则一切正常。
问题看起来像是php(with apache)不被允许连接MySQL，但是防火墙也没有。想来想去，唯有SELinux的因素会导致这个问题。
代码如下:
getsebool -a|grep -i httpd
可以看到这里设置了httpd进程的许可模式，再仔细看一下，有一个选项：
代码如下:
getsebool -a|grep -i httpd_can_network_connect
httpd_can_network_connect --> off
代码如下:
setsebool -P httpd_can_network_connect=1
代码如下:
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
# enforcing - SELinux security policy is enforced.
# permissive - SELinux prints warnings instead of enforcing.
# disabled - No SELinux policy is loaded.
#SELINUX=enforcing
#把设置改为disabled
SELINUX=disabled
# SELINUXTYPE= can take one of these two values:
# targeted - Targeted processes are protected,
# mls - Multi Level Security protection.
SELINUXTYPE=targeted
代码如下:
[root@imysql~]# setenforce 0
setenforce: SELinux is disabled
