PHP常用函数系列--换取汉字首字母

//获取汉字的首字母
function getFirstCharters($str)
{
    if (empty($str)) {
        return '';
    }
    //取出参数字符串中的首个字符
    $temp_str = substr($str,0,1);
    if(ord($temp_str) > 127){
        $str = substr($str,0,3);
    }else{
        $str = $temp_str;
        $fchar = ord($str{0});
        if ($fchar >= ord('A') && $fchar <= ord('z')){
            return strtoupper($temp_str);
        }else{
            return null;
        }
    }

    $s1 = iconv('UTF-8', 'gb2312//IGNORE', $str);
    if(empty($s1)){
        return null;
    }
    $s2 = iconv('gb2312', 'UTF-8', $s1);
    if(empty($s2)){
        return null;
    }
    $s = $s2 == $str ? $s1 : $str;

    $asc = ord($s{0}) * 256 + ord($s{1}) - 65536;

    if ($asc >= -20319 && $asc <= -20284)
        return 'A';

    if ($asc >= -20283 && $asc <= -19776)
        return 'B';

    if ($asc >= -19775 && $asc <= -19219)
        return 'C';

    if ($asc >= -19218 && $asc <= -18711)
        return 'D';

    if ($asc >= -18710 && $asc <= -18527)
        return 'E';

    if ($asc >= -18526 && $asc <= -18240)
        return 'F';

    if ($asc >= -18239 && $asc <= -17923)
        return 'G';

    if ($asc >= -17922 && $asc <= -17418)
        return 'H';

    if ($asc >= -17417 && $asc <= -16475)
        return 'J';

    if ($asc >= -16474 && $asc <= -16213)
        return 'K';

    if ($asc >= -16212 && $asc <= -15641)
        return 'L';

    if ($asc >= -15640 && $asc <= -15166)
        return 'M';

    if ($asc >= -15165 && $asc <= -14923)
        return 'N';

    if ($asc >= -14922 && $asc <= -14915)
        return 'O';

    if ($asc >= -14914 && $asc <= -14631)
        return 'P';

    if ($asc >= -14630 && $asc <= -14150)
        return 'Q';

    if ($asc >= -14149 && $asc <= -14091)
        return 'R';

    if ($asc >= -14090 && $asc <= -13319)
        return 'S';

    if ($asc >= -13318 && $asc <= -12839)
        return 'T';

    if ($asc >= -12838 && $asc <= -12557)
        return 'W';

    if ($asc >= -12556 && $asc <= -11848)
        return 'X';

    if ($asc >= -11847 && $asc <= -11056)
        return 'Y';

    if ($asc >= -11055 && $asc <= -10247)
        return 'Z';

    return rare_words($asc);
}

//百家姓中的生僻字
function rare_words($asc=''){
    $rare_arr = array(
        -3652=>array('word'=>"窦",'first_char'=>'D'),
        -8503=>array('word'=>"奚",'first_char'=>'X'),
        -9286=>array('word'=>"酆",'first_char'=>'F'),
        -7761=>array('word'=>"岑",'first_char'=>'C'),
        -5128=>array('word'=>"滕",'first_char'=>'T'),
        -9479=>array('word'=>"邬",'first_char'=>'W'),
        -5456=>array('word'=>"臧",'first_char'=>'Z'),
        -7223=>array('word'=>"闵",'first_char'=>'M'),
        -2877=>array('word'=>"裘",'first_char'=>'Q'),
        -6191=>array('word'=>"缪",'first_char'=>'M'),
        -5414=>array('word'=>"贲",'first_char'=>'B'),
        -4102=>array('word'=>"嵇",'first_char'=>'J'),
        -8969=>array('word'=>"荀",'first_char'=>'X'),
        -4938=>array('word'=>"於",'first_char'=>'Y'),
        -9017=>array('word'=>"芮",'first_char'=>'R'),
        -2848=>array('word'=>"羿",'first_char'=>'Y'),
        -9477=>array('word'=>"邴",'first_char'=>'B'),
        -9485=>array('word'=>"隗",'first_char'=>'K'),
        -6731=>array('word'=>"宓",'first_char'=>'M'),
        -9299=>array('word'=>"郗",'first_char'=>'X'),
        -5905=>array('word'=>"栾",'first_char'=>'L'),
        -4393=>array('word'=>"钭",'first_char'=>'T'),
        -9300=>array('word'=>"郜",'first_char'=>'G'),
        -8706=>array('word'=>"蔺",'first_char'=>'L'),
        -3613=>array('word'=>"胥",'first_char'=>'X'),
        -8777=>array('word'=>"莘",'first_char'=>'S'),
        -6708=>array('word'=>"逄",'first_char'=>'P'),
        -9302=>array('word'=>"郦",'first_char'=>'L'),
        -5965=>array('word'=>"璩",'first_char'=>'Q'),
        -6745=>array('word'=>"濮",'first_char'=>'P'),
        -4888=>array('word'=>"扈",'first_char'=>'H'),
        -9309=>array('word'=>"郏",'first_char'=>'J'),
        -5428=>array('word'=>"晏",'first_char'=>'Y'),
        -2849=>array('word'=>"暨",'first_char'=>'J'),
        -7206=>array('word'=>"阙",'first_char'=>'Q'),
        -4945=>array('word'=>"殳",'first_char'=>'S'),
        -9753=>array('word'=>"夔",'first_char'=>'K'),
        -10041=>array('word'=>"厍",'first_char'=>'S'),
        -5429=>array('word'=>"晁",'first_char'=>'C'),
        -2396=>array('word'=>"訾",'first_char'=>'Z'),
        -7205=>array('word'=>"阚",'first_char'=>'K'),
        -10049=>array('word'=>"乜",'first_char'=>'N'),
        -10015=>array('word'=>"蒯",'first_char'=>'K'),
        -3133=>array('word'=>"竺",'first_char'=>'Z'),
        -6698=>array('word'=>"逯",'first_char'=>'L'),
        -9799=>array('word'=>"俟",'first_char'=>'Q'),
        -6749=>array('word'=>"澹",'first_char'=>'T'),
        -7220=>array('word'=>"闾",'first_char'=>'L'),
        -10047=>array('word'=>"亓",'first_char'=>'Q'),
        -10005=>array('word'=>"仉",'first_char'=>'Z'),
        -3417=>array('word'=>"颛",'first_char'=>'Z'),
        -6431=>array('word'=>"驷",'first_char'=>'S'),
        -7226=>array('word'=>"闫",'first_char'=>'Y'),
        -9293=>array('word'=>"鄢",'first_char'=>'Y'),
        -6205=>array('word'=>"缑",'first_char'=>'G'),
        -9764=>array('word'=>"佘",'first_char'=>'S'),
        -9818=>array('word'=>"佴",'first_char'=>'N'),
        -9509=>array('word'=>"谯",'first_char'=>'Q'),
        -3122=>array('word'=>"笪",'first_char'=>'D'),
        -9823=>array('word'=>"佟",'first_char'=>'T'),
    );
    if(array_key_exists($asc, $rare_arr) && $rare_arr[$asc]['first_char']){
        return $rare_arr[$asc]['first_char'] ;
    }else{
        return null;
    }
}