PHP实现汉字或英文按照首字母查找

/** 
    * 
    */  
function getfirstchar($s0){  
               if($s0[0]=='I' || $s[0]=='i'){  
                   return "I";  
               }elseif($s0[0]=='U' || $s[0]=='u'){  
                   return 'U';  
               }elseif($s0[0]=='V' || $s[0]=='v'){  
                   return 'V';  
               }else{  
    $fchar = ord($s0{0});  
    if($fchar >= ord("A") and $fchar <= ord("z") )return strtoupper($s0{0});  
    $s1 = iconv("UTF-8","gb2312", $s0);  
    $s2 = iconv("gb2312","UTF-8", $s1);  
    if($s2 == $s0){$s = $s1;}else{$s = $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;  
               }  
    }