LNMP中PHP版本是7.1.11，為什么執(zhí)行獲取拼音方法總是502？

下面是獲取整條字符串第一個首字母代碼：

/**
 * 獲取單個漢字拼音首字母。注意:此處不要糾結(jié)。漢字拼音是沒有以U和V開頭的
 * @param $s0
 * @return null|string
 */
function getFirstChar($s0){
    error_reporting(E_ALL || ~E_NOTICE); //顯示除去 E_NOTICE 之外的所有錯誤信息
    $fchar = ord($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 >= -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 $asc <= -14150) return "Q";
    if($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;
}

/**
 * 獲取整條字符串漢字拼音首字母，包含特殊符號和數(shù)字：0~9@#￥%等
 * @param $zh
 * @return string
 */
function getCharIndex($zh){
//    error_reporting(E_ALL || ~E_NOTICE); //顯示除去 E_NOTICE 之外的所有錯誤信息
    $ret = "";
    $s1 = iconv("UTF-8","gb2312", $zh);
    $s2 = iconv("gb2312","UTF-8", $s1);
    if($s2 == $zh){$zh = $s1;}
//    for($i = 0; $i < strlen($zh); $i++){
    for($i = 0; $i < 1; $i++){
        $s1 = substr($zh,$i,1);
        $p = ord($s1);
        if($p > 160){
            $s2 = substr($zh,$i++,2);
            $ret .= getFirstChar($s2);
        }else{
            $ret .= $s1;
        }
    }
    return strtoupper($ret);
}

echo getCharIndex('測試');

服務(wù)器環(huán)境是LNMP，php版本是7.1.11，可為什么總是502