php里面的编码问题

1 获取当前字符串的编码

$encode = mb_detect_encoding($str, array("ASCII",'UTF-8',"GB2312","GBK",'BIG5'));      

2 将字符编码改为utf-8

$str_encode = mb_convert_encoding($str, 'UTF-8', $encode);      

下面举例子:把一个字符串（utf-8）编码改为gbk

$file = "C:\\Users\\Administrator\\Desktop\\中文.xls";
        $file  = iconv('utf-8', 'gb2312', $file);      

或

$file = "C:\\Users\\Administrator\\Desktop\\中文.xls";
        //自动获取字符串编码
        $encode = mb_detect_encoding($file, array("ASCII",'UTF-8',"GB2312","GBK",'BIG5'));
        $file = mb_convert_encoding($file, 'GB2312', $encode);