PHP服务器端错误“禁止您没有访问此页面的权限”

Hello everyone I have spented to much time to solve this problem but I don't found anything that that can help me even on internet and stack overflow. I found So many answer about this problem but the only problem is that I am facing this issue on my server not on my local pc.

when someone opens my page it opens correctly but after opening it 4 to 5 time it show error.

Forbidden . You don't have permission to access /mypage.php on this server.

code page 1

<form>
<input type="text" id="field1" >
<input type="text" id="field2" >
<input type="text" id="field3" >
<input type="button" id="subbtn" >
</form>

code page 2

<?php
require_once( 'parseConnect.php' );
use Parse\ParseClient;
use Parse\ParseObject;
use Parse\ParseQuery;
use Parse\ParseUser;
use Parse\ParseException;
//check if form is submitted
ob_start();
if(isset($_SESSION["loginusername"]))
{
    if(isset($_POST["submitform"])){
    $fieldvalue = $_POST['feildvalue'];
    $query = new ParseObject("table");
    $query->set("filed1332432",$filedvalue);
    $query->set("field8789",$fieldvalue);
try {
  $query->save();

  header("location:somepage2121.php#Successfull");
} catch (ParseException $ex) {

  header("location:somepage23.php#Some Error Try Again Later.".$ex->getMessage());
}
}   

}
else {
    ob_clean();
    header("location:logout.php");
}

?>

i think there is nothing to do with the code I can not post the actual code but here is some sample code page one has a basic html form and page 2 has the function to save it in the data base .. the error occur on page 2 when we post value And remember it not always.

I will suggest you please check your apache error logs to find out the exact root cause of your issues. Might be there is an issues with mod_security which is installed on your server.