CentOS安装php mbstring的扩展
yum install php*
yum install php-devel
yum install php-gd
yum install php-mcrypt
yum install php-mbstring
OK 等所有的都升级完以后，用php －m查看下加载情况：
php -m
bz2
calendar
ctype
curl
date
dbase
exif
filter
ftp
gd
gettext
gmp
hash
iconv
json
ldap
libxml
mbstring
mcrypt
memcache
mysql
mysqli
odbc
openssl
pcntl
pcre
PDO
pdo_mysql
PDO_ODBC
pdo_sqlite
posix
pspell
readline
Reflection
session
shmop
SimpleXML
sockets
SPL
standard
sysvmsg
sysvsem
sysvshm
tokenizer
wddx
xml
Zend Optimizer
zip
zlib
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看到mbstring以后重启apache，就可以了。
service httpd restart