title: PHP echo overwrites previous echo
body: <p>I have an HTML file that, when you click a button, Ajax loads a PHP file and the PHP file then echoes some text back to the HTML file.</p>
  
  <p>The problem is that if I click the button a second time (or third, or fourth, etc), the next echoes overwrite the previous echo.</p>
  
  <p>For example, if I click the button the first time, it would echo <code>text here</code>. If I click it a second time, it overwrites the previous echo and, again, would show <code>text here</code> instead of showing it on a new line.</p>
  
  <p>Here's the HTML/Ajax:
      </p>
  
  <pre><code>&lt;html&gt;
    &lt;body&gt;
      &lt;div id="show-more-results"&gt;&lt;/div&gt;
      &lt;center&gt;&lt;a class="btn show-more"&gt;Show more comments&lt;/a&gt;&lt;/center&gt;
  
      &lt;script type="text/javascript"&gt;
        var videoid = &lt;?php echo $video_id; ?&gt;;
  
        $(document).ready(function() {    
          $(".show-more").click(function() {
            num_comments += 10;
            $.ajax({
              url: 'assets/misc/test.php',
              type: "POST",
              data: {video_id: videoid, num: num_comments},
              success: function(data) {
                $("#show-more-results").html(data);
              }
            });
          });
        });
      &lt;/script&gt;
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>PHP:</p>
  
  <pre><code>&lt;?php
    $videoid = $_POST['video_id'];
    $num_comments = $_POST['num'];
  
    echo $videoid;
  ?&gt;
  </code></pre>
  
  <p>How can I make it so that the next echoes from the PHP file don't overwrite the previous echoes?</p>