php如何将unicode转换成utf-8字符

function unicodeToUTF8($str, $code = 'UTF-8') {

$str = str_replace('\u', '%u', $str);

$str = rawurldecode($str);

preg_match_all("/(?:%u.{4})|.{4};|&#\d+;|.+/U", $str, $r);

$ar = $r[0];

foreach ($ar as $k => $v) {

if (substr($v, 0, 2) == "%u") {

$ar[$k] = iconv("UCS-2", $code, pack("H4", substr($v, -4)));

} elseif (substr($v, 0, 3) == "") {

$ar[$k] = iconv("UCS-2", $code, pack("H4", substr($v, 3, -1)));

} elseif (substr($v, 0, 2) == "&#") {

echo substr($v, 2, -1) . " ";

$ar[$k] = iconv("UCS-2", $code, pack("n", substr($v, 2, -1)));

}

}

return join("", $ar);

}

echo unicodeToUTF8('选择文件');

//输出 选择文件