使用AJAX将数据发送到PHP

Question

我无法弄清楚为什么 PHP无法获取AJAX发送的数据。这是我的代码：

index.js

var receiver;
function setUser(obj){
    $("#user_inf").css({"display":"none"});
    $("#selected").attr('name', obj.value);
    $("#selected").attr('value', obj.value);
    $("#selected").html(obj.value);
    $("#selected").css({"display":"block"})
    receiver = obj.value;
    $.ajax({
        type: 'POST',
        data : {data:receiver},
        url: 'index.php',
        success: function(data){
            alert("Data sent");
        }
    });
}
function getVal(){
    return receiver;
}

index.php

<?php
    $rec = $_POST['data'];
    //include 'db.php';
    $query="SELECT *  FROM chit where sender='$myusername' and receiver='$rec' ORDER BY id";
    $run=$con1->query($query);
    while($row=$run->fetch_array()) :
?>
<div id="chat_data">
    <span style="color:green"><?php echo $row['name']?></span>:
    <span style="color:brown"><?php echo $row['message']?></span>
    <span style="float:right"><?php echo formatDate($row['date'])?></span>
</div>
<?php endwhile;?>
</div>
<div id="textarea">
  <form method="post" action="index.php">
      <input type="hidden" value="getVal()" name="receiver">
      <textarea type="text" name="message" id="message"></textarea>
      <input type="checkbox" name="veb" id="via">
      <label id="chktxt">Via Executive Board</label>
      <input type="button" id="sndmsg" name="submit" value="SEND" onclick="">
  </form>
</div>
<?php
  if(isset($_POST['submit']))
  {
    $sender=$myusername;
    $receiver=$_POST['receiver'];
    $message=$_POST['message'];
    $eb=$_POST['veb'];
    $query="INSERT INTO CHIT (sender,receiver,message,eb)values ('$sender','$receiver','$message','$eb')";
    $run = $con1->query($query);
    if($run)
      echo "<embed loop='false' src='chat.wav' hidden='true' autoplay='true'/>";
  }
?>

这是我得到的错误 致命错误：未捕获错误：在C：\ xampp \ htdocs \ chat \ home.php中调用boolean上的成员函数fetch_array（）：84堆栈跟踪：＃0 {main}抛出 C：\ xampp \ htdocs \ chat \ home.php 在线 2

另外：该表单在网页中的任何位置都不可见。它甚至不在页面的源代码中。