用PHP提取中英文词语以及数字的首字母的方法介绍

最近项目有个需求，在一个中英文（包括阿拉伯数字0-9）的海量词库中，提取每一个词语的首字母：

gannicus——>G

自由自在——>Z

2B——>E

傻X——>S
代码如下:
private function getfirstchar($s0){
        $s=iconv('UTF-8','gb2312', $s0);
        if (ord($s0)>128) { //汉字开头
            $asc=ord($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 $asc<=-17418)return "I";             
            if($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";