best way to communicate between php and jquery/javascript

At first, you’ll have to make a dropdown filled with your values from the database:

<select id="pakket">
  <?php
    foreach ($allPakkets as $pakket) {
      echo '<option value="'.$pakket['id'].'">'.$pakket['name'].'</option>';
    }
  ?>
</select>

And a div to put results in:

<div id="results"></div>

Now, we add a piece of javascript:

jQuery('#pakket').change(function(){ // when the dropdown changes...
  var newvalue = jQuery('#pakket').val(); // get the new value
  jQuery.ajax({
    method: 'GET',
    url: 'url-to-script.php',
    data: {
      newvalue: newvalue
    }
  }).done(function(response){ // after the request has been loaded...
    jQuery('#results').html(response); // put the response in the div
  });
});

Now the only thing you have to do is make a url-to-script.php which loads the properties of the value sent in $_GET['newvalue']. The output of this PHP script will be placed in the div#results.