php汉字转拼音首字母有关问题

php汉字转拼音首字母问题。
程序运行后，发现字符串中有些文字转换不了。如果是单独输入这些字，直接去转换可以读取出拼音开头字母。
在字符串中就不行。程序代码如下：

function getfirstchar($s0){

$fchar = ord($s0{0});

if($fchar >= ord("a") and $fchar <= ord("Z") )return strtoupper($s0{0});

$s1 = iconv("UTF-8","gb2312", $s0);

$s2 = iconv("gb2312","UTF-8", $s1);

if($s2 == $s0){$s = $s1;}else{$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";

return null;

}

function pinyin1($zh){

$ret = "";

$s1 = iconv("UTF-8","gb2312", $zh);

$s2 = iconv("gb2312","UTF-8", $s1);

if($s2 == $zh){$zh = $s1;}

for($i = 0; $i < strlen($zh); $i++){

$s1 = substr($zh,$i,1);

$p = ord($s1);

if($p > 160){

$s2 = substr($zh,$i++,2);

$ret .= getfirstchar($s2);

}else{

$ret .= $s1;

}

}

return $ret;