将值从php页面传递到其他页面的模态

I'm trying to edit a post using this snippiet of from my query.php page:

echo '<button type="submit"  onclick="openModal(this)" id="btn-edit"
name="edit" value='.$postID.'></button>';


function openModal(id)
{
    var editpost = id.value;
        $.ajax({
            url:"query.php",
            method:"POST",
            data:{ editpost : editpost },
            success:function(data)
            { //
            },
            error: function () {//
            }
        });
    $('#edit').modal('show');
}

The function to get the data from the post selected is on the same php page. This is the code:

if(isset($_POST['editpost'])) 
{
    session_start();
    $editpostid = $_POST['editpost'];

    if($editpostid != "")
    {
        $sql = "SELECT * FROM post WHERE PostId = '" . $editpostid . "'";
    }

    if($sql != "")
    {
        $qry = mysqli_query($connection, $sql);
        if (mysqli_num_rows($qry) > 0) 
        {
            foreach($qry as $row)
            {
                $_SESSION['editpostdesc'] = $row['PostDesc'];
                $_SESSION['editpostfile'] = $row['PostFile'];
                $_SESSION['editpostid'] = $row['PostId'];
            }
        }
    }
}

But the modal is on the other page (main page). I want to get the data of the post and display it on the modal, so I tried using $_SESSION. Yes, I got the data and was able to display it on the modal, but the problem is when I try to edit another post, the first value assigned to the session cannot be replaced. Is there is any other way that I can pass the values without using session? I'm really running out of ideas, I'm just starting my first web project.

if you get multiple row means this methods will worked...

if(isset($_POST['editpost'])) 
{
    session_start();
    $editpostid = $_POST['editpost'];

    if($editpostid != "")
    {
        $sql = "SELECT * FROM post WHERE PostId = '" . $editpostid . "'";
    }

    if($sql != "")
    {
        $qry = mysqli_query($connection, $sql);
        if (mysqli_num_rows($qry) > 0) 
        {
            foreach($qry as $row)
            {
                $res[] = array(
                                'editpostdesc' => $row['PostDesc'],
                                'editpostfile' => $row['PostFile'],
                                 'editpostid'  => $row['PostId']
                               ); 
            }


        }
    }
}