php 实现 从unicode到gb2312的转换

php 实现 从unicode到gb2312的转换，代码如下

$a="/u53D1/u8868/u8BC4/u8BBA/uFF1A";
echo unicode2gb2312($a);


//将/uXXXX/uXXXX...等的编码形式转换为gb2312字符串
function unicode2gb2312($str) {
$bs = split('/u',$str);
$c = "";
for($i = 1; $i < count($bs); $i++) {
$c .= chr(hexdec(substr($bs[$i],2)));
$c .= chr(hexdec(substr($bs[$i],0,2)));
}
$c = iconv('UTF-16', 'GB2312', $c);
return $c;
}