今天项目升级到php5.4，gbk编码，htmlspecialchars转换后的字符串为空，郁闷啊

解决，加上编码吧，这么多地方用到htmlspecialchars，改起来真麻烦，看来以后得自己封装一下了。

UPGRADING说到
[html]
- the default character set for htmlspecialchars() and htmlentities() is 
  now UTF-8. In previous versions it was ISO-8859-1. Note that changing 
  your output charset via the php.ini default_charset directive does not 
  affect htmlspecialchars/htmlentities unless you are passing "" (an  
  empty string) as the encoding parameter to your htmlspecialchars/htmlentities 
  calls.  

手册中也说到

[html] 
string htmlspecialchars ( string $string [, int $flags = ENT_COMPAT | ENT_HTML401 [, string $encoding = 'UTF-8' [, bool $double_encode = true ]]] ) 

[html] 
Defines encoding used in conversion. If omitted, the default value for this argument is ISO-8859-1 in versions of PHP prior to 5.4.0, and UTF-8 from PHP 5.4.0 onwards.