搜索引擎：Php从anchor-tag获取数据

I have this html search here:

      <form action="index.php" method="POST">
      <input id="search" type="text" placeholder="Search for Friends" name="search_name">
      <input class="submit" type="submit" name="search-submit" value="Search">
      </form>

And this php code for the search engine:

<?php
  if (isset($_POST['search-submit'])) {
   $search_name = $_POST['search_name'];
   $aVar = mysqli_connect('localhost','root','','socialnetwork');
   $result = mysqli_query($aVar, "SELECT username FROM users WHERE username LIKE '%$search_name%'");
   $found = 1;
   while ($row = mysqli_fetch_assoc($result)) {
     $username = $row['username'];
     @$output .= '<h2 class="friends-display"><a href="">'.$username.'</a></h2><hr>'; 
   }
 }

 ?>

Now this code is working fine. It allows the user to search for other users. The anchor tag "friends-display" shows the result of the code by using the variable $output. The $output is then echoed later in the aside.

My problem is the following: I want to make an if-statement so when the anchor tag "friends-display" is clicked by the user it should show the profile of the username the user has clicked on.

Example: you search for Mike and you find this username. Than you click on it and it should show the profile of Mike. How can I make this with an anchor tag?

I have tried if isset(), but it did not work for me.

</div>

Change the output variable like below

....
while ($row = mysqli_fetch_assoc($result)) { 
    $username = $row['username'];
     @$output .= '<h2 class="friends-display"><a href="profile.php?user='.$username.'">'.$username.'</a></h2><hr>'; 
}
....

Create a new file profile.php and add the following basic line.

<?php
If(isset($_GET['user']) && !empty($_GET['user'])){
    $username = $_GET['user'];
    // check for username found in database. 
    // if not found exit with error "user not found"
    // else show user profile
}else{
    Die("unothrized access");
}

I hope this will guide you to achieve your target.. Happy coding :)