PHPで漢字の最初の文字を大文字にする方法

<?php
 
function getfirstchar($s0) {
    $fchar = ord(substr($s0, 0, 1));
    if (($fchar >= ord("a") and $fchar <= ord("z"))or($fchar >= ord("A") and $fchar <= ord("Z"))) return strtoupper(chr($fchar));
    $s = iconv("UTF-8", "GBK", $s0);
    $asc = ord($s{0}) * 256 + ord($s{1})-65536;
    if ($asc >= -20319 and $asc <= -20284)return "A";
    if ($asc >= -20283 and $asc <= -19776)return "B";
    if ($asc >= -19775 and $asc <= -19219)return "C";
    if ($asc >= -19218 and $asc <= -18711)return "D";
    if ($asc >= -18710 and $asc <= -18527)return "E";
    if ($asc >= -18526 and $asc <= -18240)return "F";
    if ($asc >= -18239 and $asc <= -17923)return "G";
    if ($asc >= -17922 and $asc <= -17418)return "H";
    if ($asc >= -17417 and $asc <= -16475)return "J";
    if ($asc >= -16474 and $asc <= -16213)return "K";
    if ($asc >= -16212 and $asc <= -15641)return "L";
    if ($asc >= -15640 and $asc <= -15166)return "M";
    if ($asc >= -15165 and $asc <= -14923)return "N";
    if ($asc >= -14922 and $asc <= -14915)return "O";
    if ($asc >= -14914 and $asc <= -14631)return "P";
    if ($asc >= -14630 and $asc <= -14150)return "Q";
    if ($asc >= -14149 and $asc <= -14091)return "R";
    if ($asc >= -14090 and $asc <= -13319)return "S";
    if ($asc >= -13318 and $asc <= -12839)return "T";
    if ($asc >= -12838 and $asc <= -12557)return "W";
    if ($asc >= -12556 and $asc <= -11848)return "X";
    if ($asc >= -11847 and $asc <= -11056)return "Y";
    if ($asc >= -11055 and $asc <= -10247)return "Z";
    return null;
}
 
function mb_str_split($string) {
    return preg_split(&#39;/(?<!^)(?!$)/u&#39;, $string);
}
 
function get_letter($string) {
    $charlist = mb_str_split($string);
    return implode(array_map("getfirstchar", $charlist));
}
echo get_letter("刹车片");
?>

SCP