How to implement a custom function in PHP to obtain the first letter of a Chinese character

<?php
/*
* Created on 2016-12-1
*/
function getFirstCharter($str)
{
  if (empty($str)) {
    return &#39;&#39;;
  }
  $fchar = ord($str{0});
  if ($fchar >= ord(&#39;A&#39;) && $fchar <= ord(&#39;z&#39;))
    return strtoupper($str{0});
  $s1 = iconv(&#39;UTF-8&#39;, &#39;gb2312&#39;, $str);
  $s2 = iconv(&#39;gb2312&#39;, &#39;UTF-8&#39;, $s1);
  $s = $s2 == $str ? $s1 : $str;
  $asc = ord($s{0}) * 256 + ord($s{1}) - 65536;
  if ($asc >= -20319 && $asc <= -20284)
    return &#39;A&#39;;
  if ($asc >= -20283 && $asc <= -19776)
    return &#39;B&#39;;
  if ($asc >= -19775 && $asc <= -19219)
    return &#39;C&#39;;
  if ($asc >= -19218 && $asc <= -18711)
    return &#39;D&#39;;
  if ($asc >= -18710 && $asc <= -18527)
    return &#39;E&#39;;
  if ($asc >= -18526 && $asc <= -18240)
    return &#39;F&#39;;
  if ($asc >= -18239 && $asc <= -17923)
    return &#39;G&#39;;
  if ($asc >= -17922 && $asc <= -17418)
    return &#39;H&#39;;
  if ($asc >= -17417 && $asc <= -16475)
    return &#39;J&#39;;
  if ($asc >= -16474 && $asc <= -16213)
    return &#39;K&#39;;
  if ($asc >= -16212 && $asc <= -15641)
    return &#39;L&#39;;
  if ($asc >= -15640 && $asc <= -15166)
    return &#39;M&#39;;
  if ($asc >= -15165 && $asc <= -14923)
    return &#39;N&#39;;
  if ($asc >= -14922 && $asc <= -14915)
    return &#39;O&#39;;
  if ($asc >= -14914 && $asc <= -14631)
    return &#39;P&#39;;
  if ($asc >= -14630 && $asc <= -14150)
    return &#39;Q&#39;;
  if ($asc >= -14149 && $asc <= -14091)
    return &#39;R&#39;;
  if ($asc >= -14090 && $asc <= -13319)
    return &#39;S&#39;;
  if ($asc >= -13318 && $asc <= -12839)
    return &#39;T&#39;;
  if ($asc >= -12838 && $asc <= -12557)
    return &#39;W&#39;;
  if ($asc >= -12556 && $asc <= -11848)
    return &#39;X&#39;;
  if ($asc >= -11847 && $asc <= -11056)
    return &#39;Y&#39;;
  if ($asc >= -11055 && $asc <= -10247)
    return &#39;Z&#39;;
  return null;
}
$firstChar = getFirstCharter(&#39;脚本之家&#39;);
print_r($firstChar);//输出：J
?>