$str = iconv(‘UTF-8′, ‘GBK//IGNORE’, unescape(isset($_GET['str'])? $_GET['str']:”));
If you append the string //IGNORE, characters that cannot be represented in the target charset are silently discarded. Otherwise, str is cut from the first illegal character.
If you append the string //TRANSLIT to out_charset transliteration is activated. This means that when a character can’t be represented in the target charset, it can be approximated through one or several similarly looking characters.

本地测试//IGNORE能忽略掉它不认识的字接着往下转，并且不报错，而//TRANSLIT是截掉它不认识的字及其后面的内容，并且报错。//IGNORE是我需要的。

1. 发现iconv在转换字符”-”到gb2312时会出错，如果没有ignore参数，所有该字符后面的字符串都无法被保存。不管怎么样，这个”-”都无法转换成功，无法输出。另外mb_convert_encoding没有这个bug.
2. mb_convert_encoding 可以指定多种输入编码，它会根据内容自动识别,但是执行效率比iconv差太多；如：$str = mb_convert_encoding($str,”euc-jp”,”ASCII,JIS,EUC-JP,SJIS,UTF- 8″);“ASCII,JIS,EUC-JP,SJIS,UTF-8”的顺序不同效果也有差异
3. 一般情况下用 iconv，只有当遇到无法确定原编码是何种编码，或者iconv转化后无法正常显示时才用

string mb_convert_encoding ( string str, string to_encoding [, mixed from_encoding] )
需要先启用 mbstring 扩展库
from_encoding is specified by character code name before conversion. it can be array or string – comma separated enumerated list. If it is not specified, the internal encoding will be used.

$str = mb_convert_encoding($str, “UCS-2LE”, “JIS, eucjp-win, sjis-win”);
$str = mb_convert_encoding($str, “EUC-JP’, “auto”);

例子：
$content = iconv(“GBK”, “UTF-8//IGNORE”, $content);
$content = mb_convert_encoding($content, “UTF-8″, “GBK”);

最后总结， iconv(“GBK”, “UTF-8//IGNORE”, $content)仍然会报错，mb_convert_encoding($content, “UTF-8″, “GBK”)不报错。