php取出字符串（包括汉字）首字母函数

<?php
//取出首字母函数

function getfirstchar($s0){ 
if(ord($s0)>="1" and ord($s0)<=ord("z") )   { return strtoupper($s0); } 
//$s=iconv("UTF-8","gb2312", $s0); 如果需要转换为utf-8的话
$s=$s0;//无需转换的情况
$asc=ord($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 0; 
}
echo getfirstchar("你好");

?>