PHP mnemonic code full text 400 words to extract the first letter of each Chinese character

Mnemonic code ： similar ,
Xiao Ming ------XM ,
Xiaohong -------XH,
Xiaoyun ------XY,

The following is the code implementation ：

<?php
// Definition 
$str = ' I am a good person ';
function mbstringtoarray($str, $charset)
{
    
    $strlen = mb_strlen($str);
    while ($strlen) {
    
        $array[] = mb_substr($str, 0, 1, $charset);
        $str = mb_substr($str, 1, $strlen, $charset);
        $strlen = mb_strlen($str);
    }
    return $array;
}
$arr = mbstringtoarray($str, "utf-8");
//print_r($arr);
// You can get the first letter of the first word of a sentence 
function getFirstCharter($str)
{
    
    if (empty($str)) {
    
        return '';
    }
    $fchar = ord($str{
    0});
    if ($fchar >= ord('A') && $fchar <= ord('z')) return strtoupper($str{
    0});
    $s1 = iconv('UTF-8', 'gb2312', $str);
    $s2 = iconv('gb2312', 'UTF-8', $s1);
    $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 && $asc <= -10247) return 'Z';
    return null;
}
// Test functions getFirstCharter Output result 
//echo getFirstCharter($str);
foreach ($arr as $k => &$v) {
    
    echo $v = getFirstCharter($v);
}