实现方法如下

<?php

/**
 * @author Tech
 */
class Character
{
 /**
  * 二维数组根据首字母分组排序
  * @param array $data  二维数组
  * @param string $targetKey 首字母的键名
  * @return array    根据首字母关联的二维数组
  */
 public function groupByInitials(array $data, $targetKey = 'name')
 {
  $data = array_map(function ($item) use ($targetKey) {
   return array_merge($item, [
    'initials' => $this->getInitials($item[$targetKey]),
   ]);
  }, $data);
  $data = $this->sortInitials($data);
  return $data;
 }

 /**
  * 按字母排序
  * @param array $data
  * @return array
  */
 public function sortInitials(array $data)
 {
  $sortData = [];
  foreach ($data as $key => $value) {
   $sortData[$value['initials']][] = $value;
  }
  ksort($sortData);
  return $sortData;
 }
 
 /**
  * 获取首字母
  * @param string $str 汉字字符串
  * @return string 首字母
  */
 public function getInitials($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;
 }

}

项目中直接引入即可，如果需要命名空间，可以自行添加，下面是我们看看怎么用。

// 按首字母排序
$data = [
 ['id' => 1, 'area_name' => '山东'],
 ['id' => 2, 'area_name' => '江苏'],
 ['id' => 3, 'area_name' => '安徽'],
 ['id' => 4, 'area_name' => '福建'],
 ['id' => 5, 'area_name' => '江西'],
 ['id' => 6, 'area_name' => '广东'],
 ['id' => 7, 'area_name' => '广西'],
 ['id' => 8, 'area_name' => '海南'],
 ['id' => 9, 'area_name' => '河南'],
 ['id' => 10, 'area_name' => '湖南'],
 ['id' => 11, 'area_name' => '湖北'],
];
// 初始化，然后调用分组方法
$data = (new Character)->groupByInitials($data, 'area_name');

下面的结果是不是你想要的呢，不论是做app还是网页，都可以用

$data = array(
 'A' => array(
  0 => array(
   'id' => 3,
   'area_name' => '安徽',
   'initials' => 'A'
  )
 ) ,
 'F' => array(
  0 => array(
   'id' => 4,
   'area_name' => '福建',
   'initials' => 'F'
  )
 ) ,
 'G' => array(
  0 => array(
   'id' => 6,
   'area_name' => '广东',
   'initials' => 'G'
  ) ,
  1 => array(
   'id' => 7,
   'area_name' => '广西',
   'initials' => 'G'
  )
 ) ,
 'H' => array(
  0 => array(
   'id' => 8,
   'area_name' => '海南',
   'initials' => 'H'
  ) ,
  1 => array(
   'id' => 9,
   'area_name' => '河南',
   'initials' => 'H'
  ) ,
  2 => array(
   'id' => 10,
   'area_name' => '湖南',
   'initials' => 'H'
  ) ,
  3 => array(
   'id' => 11,
   'area_name' => '湖北',
   'initials' => 'H'
  )
 ) ,
 'J' => array(
  0 => array(
   'id' => 2,
   'area_name' => '江苏',
   'initials' => 'J'
  ) ,
  1 => array(
   'id' => 5,
   'area_name' => '江西',
   'initials' => 'J'
  )
 ) ,
 'S' => array(
  0 => array(
   'id' => 1,
   'area_name' => '山东',
   'initials' => 'S'
  )
 )
);