What are the implementations of sending push notifications to an Android application?

Question

Android

I am making an application that should receive push notification messages. I use Firebase for push notifications . Messages are sent from the program under windows to the database on the server and notifications are sent. The problem is that notifications do not always arrive instantly (sometimes with a very long delay). Interested in how sending and receiving notifications are arranged in popular instant messengers.

Answer 1

You will need LIMIT and OFFSET
Query

SELECT * FROM `video` ORDER BY 'id' LIMIT 5 OFFSET 10

will return the results from eleventh to fifteenth. Limit = how many results to select, offset - how many to skip.

$results_per_page = 19;
$page = isset($_REQUEST['page']) ? intval($_REQUEST['page']) : 1; // если страница не указана, то будет 1
$limit = $results_per_page;
$offset = $results_per_page * ($page - 1); // для вторй страницы отступ будет 19, для третьей - 38 и так далее.

Answer 2

Link example localhost?limit=19&offset=0
limit - Number of videos
offset- offset

<?PHP
    $offset = isset($_GET["offset"])?$_GET["offset"]:0;
    $limit = isset($_GET["limit"])?$_GET["limit"]:19;
    $movie = mysqli_query($connection, "SELECT * FROM `video` ORDER BY 'id' LIMIT ".$limit." OFFSET ".$offset);
  $mov = array();
  while($row = mysqli_fetch_array($movie))
      array_push($mov,$row);
    
    foreach ($mov as $m): ?>
              <li>
              	<div class="desc">
                  <a href="#">
                  	<img src="media/img/<?php echo $m['img'].'.jpg' ?>" width="240" height="160"/>
                 	 	<span class="vieo_time"></span></a>
              </div>   	 	

                    <div class="video_name">
                        <a href="#" title="<?php echo $m['title']; ?>"><?php echo $m['title']; ?></a></div>
                  <span class="views">Просмотров: <?php echo $m['views']; ?></span>

              </li>
           <?php endforeach; ?>
           
<div id="page">
  <ul>
     <?php
        
    $res = mysqli_query($connection, "SELECT CEILING(COUNT(id)/".$limit.") FROM video");
      $len = mysqli_fetch_row($res)[0];
      for($i = 0; $i < $len; $i++)
    		echo "<li><a href='?limit=$limit&offset=".($limit*$i)."'>". ($i + 1)." </a></li>";
  		 ?>
  </ul>
</div>