php转换字符串编码

    /**
     * 转换字符串编码
     * @param  String $string 要编码的字符串
     * @param  String $encoding 要转换成的编码类型 参考：mbstring模块支持的编码
     * @return String 编码后的字符串
     */
    function str_encoding_convert($string,$encoding='UTF-8'){
        $encoding_list = array('UTF-8','ASCII','GBK','GB2312','GB18030','BIG5');
        $string_encoding = mb_detect_encoding($string,'auto');
        $encoding = strtoupper($encoding);
        // 判断是否等同所设置编码
        if ($string_encoding === $encoding) {
            return $string;
        }else{
            if (function_exists('mb_convert_encoding')) {
                return mb_convert_encoding($string,$encoding,$encoding_list);
            }else{
                return iconv($string_encoding,$encoding.'//IGNORE',$string);
            }
        }
    }