?php 
  require_once './db_conn.php';
  $sql = "select * from user";
  $result = mysqli_query($conn, $sql);
?>
html lang="zh-CN">
head>
  meta charset="UTF-8">
  title>全选演示/title>
  meta http-equiv="X-UA-Compatible" content="IE=Edge">
  link rel="stylesheet" type="text/css" href="./static/bootstrap.min.css" rel="external nofollow" >
  script src="./static/jquery.js">/script>
  meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0">
/head>
body>
  form enctype="multipart/form-data" method="post">
    div class="bs-example" data-example-id="simple-table" style="padding-left: 30px;">
      table class="table" id="J-dl">
        a href="javascript:void(0);" rel="external nofollow" class="btn btn-danger" onclick="selectAll()" title="删除选定数据" style="font-weight:normal">批量删除/a>
        thead>
          tr>
            th>input type="checkbox" id="J-all" class="ckb">/th>
            th>First Name/th>
            th>Last Name/th>
            th>Username/th>
          /tr>
        /thead>
        tbody>
          ?php 
          while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
            echo  'tr>
            th>input type="checkbox" class="ck" id="ck-1" value="'.$row['id'].'">/th>
            th scope="row">'.$row['id'].'/th>
            td>'.$row['username'].'/td>
            td>'.$row['sort'].'/td>
            /tr>';
          }
          ?>
        /tbody>
      /table>
    /div>  
  /form>
  script>
    (function () {
      var $all = $('#J-all');
      var $dl = $('#J-dl');

      // 绑定全选按钮点击事件，让下面所有的复选框是跟全选的一样
      $all.on('click', function () {
        $dl.find('.ck').prop('checked', !!this.checked);
      });

      // 绑定点击所有的复选框，点击的时候判断是否页面中全选了
      $dl.find('.ck').on('click', function () {
        // 我只是喜欢用filter(fn),用选择器也行
        // 查找没有选择的元素
        var $unSelectedElem = $dl.find('.ck').filter(function () {
          return !this.checked;
        });

        // 如果有没有选中的，则让全选的取消
        if ($unSelectedElem.length) {
          $all.prop('checked', false);
        }
        else {
          $all.prop('checked', true);
        }
      });
    })();
  /script>
  script type="text/javascript">
    function selectAll() {
      var ids = '';
      $(".ck").each(function() {
        if ($(this).is(':checked')) {
          ids += ',' + $(this).val(); //逐个获取id值，并用逗号分割开
      }
    });
    ids = ids.substring(1); // 进行id处理，去除第一位的逗号
    if (ids.length == 0) {
      alert('请至少选择一项');
    } else {
      if (confirm("确定删除选中的？")) {
        $.ajax({
          type: "post",
          url: "piliangdo.php",
          data: {
            ids:ids
          },
          success: function(data) {
            if(data.trim()=="yes")
            {
              alert("删除成功");
              location.reload() //刷新页面
            }
            else
            {
              alert("删除失败");
            }
          }
        });
      }
    }
  }
  /script>
/body>
/html>

?php 
  header("content-type:text/html;charset='utf-8'");
  require_once './db_conn.php';
  
  $ids = trim($_POST['ids']);
  $ids = explode(',', $ids);
  foreach ($ids as $key => $val) {
     $del_sql = "DELETE FROM `user` WHERE id = '$val'";
     $result = mysqli_query($conn, $del_sql);
  }
  if ($result) {
    echo "yes";
  }
  else{
     echo "no";
  }
?>