How to show comments on specific posts

Question

I have an application that where users can post announcements and comment on posts. My problem is that whenever a comment is posted, It shows up on every announcement post. How can I post comments so that they show up on that specific post?

I have 2 database tables: "announcement: id, name, announcementTitle, announcement, image" and "comment: id, post_id, name, comment" with foreign key attached to comment.

Here is my home.php where the announcements and comments are echoed

<div class="container">
            <div class="mx-auto">
                <?php 
                if (isset($_SESSION['username'])) {
                
                    echo'
                <h1 style="text-decoration:underline">Post an announcement</h1>
                <form method="post" action="announcement.php" enctype="multipart/form-data">
                    <input type="text" name="announcementTitle" placeholder="Enter Subject"><br>
                    <textarea name="announcementBox" rows="5" cols="40" placeholder="Enter Announcement"></textarea><br>
                    <input type="file" name="image" accept="image/jpeg">
                    <button name="announcement">Submit</button>
                </form>';
                    
                }
                $query = "SELECT * FROM announcement ORDER BY id DESC";
                $result = mysqli_query($con,$query);
                while ($row = mysqli_fetch_array($result)) {
                    echo '<div class="row" style="color:black;background-color:white;border-radius:5px;padding:10px;margin-top:10px;margin-bottom:70px">';
                    echo '<div class="column" style="width:100%;border:5px">';
                    if (isset($_SESSION['username'])) {
                        
                        echo '<form method="post" action="announcement.php">';
                        echo "Posted by " .$row["name"]. " click X to delete:";
                        echo '<input type="hidden" name="postID" value="'.$row['id'].'">';
                        echo '<button name="delete" style="float:right">X</button>';
                        echo '</form>';
                    
                    }
                    echo $row['announcementTitle'].'<br>';
                    echo $row['announcement'].'<br>';
                    echo '<img width="20%" src="data:image;base64,'.$row['image'].'"alt="Image" style="padding-top:10px">';
                    echo'
                    <form method="post" action="comment.php">
                        <textarea name="commentbox" rows="2" cols="50" placeholder="Leave a Comment"></textarea><br>
                    
                        <button name="comment">Submit</button>
                    </form>';
                    echo "Comments:<p><p>";
                    echo " <p>";
                    $find_comment = "SELECT * FROM comment ORDER BY id DESC";
                    $res = mysqli_query($con,$find_comment);
                    while ($row = mysqli_fetch_array($res)) {
                        echo '<input type="hidden" name="postID" value="'.$row['post_id'].'">';
                        $comment_name = $row['name'];
                        $comment = $row['comment'];
                        echo "$comment_name: $comment<p>";
                    }
                    if(isset($_GET['error'])) {
                        echo "<p>100 Character Limit";
                    }
                    echo '</div></div>';
                
                    }
                
                ?>
            </div>
        </div>

Here is comment.php where comments are put in the database

<?php

session_start();


$con = mysqli_connect('localhost', 'root', 'Arv5n321');

mysqli_select_db($con, 'userregistration');

$namee = '';
$comment = '';

$comment_length = strlen($comment);

if($comment_length > 100) {
    header("location: home.php?error=1");
}else {
    $que = "SELECT * FROM announcement";
    $res = mysqli_query($con,$que);
    while ($row = mysqli_fetch_array($res)) {
        $post_id = $row['id'];
    }
    $namee = $_SESSION['username'];
    $comment = $_POST['commentbox'];
    $query = "INSERT INTO comment(post_id,name,comment) VALUES('$post_id','$namee','$comment')";
    $result = mysqli_query($con, $query);
    if ($result) {
    header("location:home.php?success=submitted");
    } else {
        header("location:home.php?error=couldnotsubmit");
    }
}



?>

Here is announcement.php where announcements are put in the database

<?php
session_start();
//$con = mysqli_connect('freedb.tech', 'freedbtech_arvindra', 'Arv5n321', 'freedbtech_remote') or die(mysqli_error($con));
$con = mysqli_connect('localhost', 'root', 'Arv5n321', 'userregistration') or die(mysqli_error($con));

if (isset($_POST['announcement'])) {
    $image = $_FILES['image']['tmp_name'];
    $name = $_FILES['image']['name'];
    $image = base64_encode(file_get_contents(addslashes($image)));
    date_default_timezone_set("America/New_York");
    $title = $_POST['announcementTitle']." (<b>".date("m/d/Y")." ".date("h:i:sa")."</b>)";
    $paragraph = $_POST['announcementBox'];
if (empty($paragraph)||empty($title)) {
    header('location:home.php?error=fillintheblanks');

}else{
    $nam = $_SESSION['username'];
    $query = "insert into announcement(name,announcementTitle,announcement,image) values('$nam','$title','$paragraph','$image')";
    $result = mysqli_query($con, $query);
    if ($result) {
    header("location:home.php?success=submitted");
    } else {
        header("location:home.php?error=couldnotsubmit");
    }
}
}else if (isset($_POST['delete'])){
    $query = "delete from announcement where id='".$_POST['postID']."';";
    $result = mysqli_query($con,$query);
    if ($result) {
        header('location:home.php?success=deleted');
    } else {
        header('location:home.php?error=couldnotdelete');
    }
}
    else {
    header('location:home.php');
}

I am a little new to PHP so any help is good.