php 中文字符串首字母的获取函数分享

代码如下:
function chineseFirst($str)
{

    $str= iconv("UTF-8","gb2312", $str);    //如果程序是gbk的，此行就要注释掉

    //判断字符串是否全都是中文
    if (preg_match("/^[\x7f-\xff]/", $str))
    {
        $fchar=ord($str{0});  
        if($fchar>=ord("A") and $fchar<=ord("z") )return strtoupper($str{0});
        $a = $str;
        $val=ord($a{0})*256+ord($a{1})-65536;
        if($val>=-20319 and $val<=-20284)return "A";  
        if($val>=-20283 and $val<=-19776)return "B";  
        if($val>=-19775 and $val<=-19219)return "C";  
        if($val>=-19218 and $val<=-18711)return "D";  
        if($val>=-18710 and $val<=-18527)return "E";  
        if($val>=-18526 and $val<=-18240)return "F";  
        if($val>=-18239 and $val<=-17923)return "G";  
        if($val>=-17922 and $val<=-17418)return "H";
        if($val>=-17417 and $val<=-16475)return "J";                
        if($val>=-16474 and $val<=-16213)return "K";                
        if($val>=-16212 and $val<=-15641)return "L";                
        if($val>=-15640 and $val<=-15166)return "M";                
        if($val>=-15165 and $val<=-14923)return "N";                
        if($val>=-14922 and $val<=-14915)return "O";                
        if($val>=-14914 and $val<=-14631)return "P";                
        if($val>=-14630 and $val<=-14150)return "Q";                
        if($val>=-14149 and $val<=-14091)return "R";                
        if($val>=-14090 and $val<=-13319)return "S";                
        if($val>=-13318 and $val<=-12839)return "T";                
        if($val>=-12838 and $val<=-12557)return "W";                
        if($val>=-12556 and $val<=-11848)return "X";                
        if($val>=-11847 and $val<=-11056)return "Y";                
        if($val>=-11055 and $val<=-10247)return "Z";
    } else
    {
        return false;
    }

}