汉字转换拼音的有关问题

汉字转换拼音的问题
想要把汉字的首字母提出来，网上搜到下面这个函数，不过让人很郁闷的是很多较为不常用的汉字无法识别，例如饽、窦、鹬...等等。不知道该如何解决。

PHP code

function getfirstchar($s0){ 
        $firstchar_ord=ord(strtoupper($s0{0})); 
        if (($firstchar_ord>=65 and $firstchar_ord<=91)or($firstchar_ord>=48 and $firstchar_ord<=57)) return $s0{0}; 
        $s0=iconv("UTF-8","gb2312", $s0);
        $s=$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"; 
    }