获取汉字首字母

使用情景:
需要按照名称首字母排序,但是又没有填写首字母的输入框,所以就在后端获取输入的文字的首字母,将首字母也一起插入数据库,

• 样例输入: 张三
• 样例输出: Z

亲测有效

/**
 * 获取汉字的首字母
 */
public 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 $this->rare_words($asc);
}
/**
 * 百家姓中的生僻字
 */
public 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;
    }
}