过滤表从数据库php显示

I have 2 tables in my db: Campaigns and Logs.In Campaigns table, these are 2 columns: campaignName and campaignSource. In the website, I want to have a filter that shows the campaignName. But when user chooses the campaignName, it should give the campaignSources and logs related to THAT campaignName.

Here is the form code:

<div class="collapse" id="network-button">

        <form method="POST" action="index.php">
        <?php 


            include "db.php";
            $result = $db -> query("SELECT * FROM Campaigns");
            $campaigns = $result -> fetch_all(MYSQLI_ASSOC);
            echo '<select class="selectpicker" data-live-search="true" name="campaings">';
            foreach ($campaigns as $campaign){

                echo '<option value='.$campaign['campaignSource'].'>'.$campaign['campaignName'].'</option>';
            }
            echo '</select>';
            echo '<button id="campaign-filter" type="submit">FILTER</button>';
        ?>
        </form>
  </div>

Here is the data will be printed on website, php code:

$result = $db -> query("SELECT * FROM Log WHERE campaignSource= '' "); 

$log = $result -> fetch_all(MYSQLI_ASSOC);

foreach($log as $mylog) {
echo "<tr role='row'>";
echo "<td>";
echo $mylog["campaignSource"];
echo "</td>";
echo "</tr>";
echo "<td>";
echo $mylog["appID"];
echo "</td>";
echo "<td>";
echo $mylog["appName"];
echo "</td>";
  } 

Its not filtering now. Thank you if you can help me to see through the problem