PHP成功后终止HTML，而不是错误

Question

<?php
    if (isset($_GET['key']) && isset($_GET['username'])) {
        $activationQuery = "SELECT activationKey FROM users WHERE username = :username"; 
        $activationQueryParams = array(':username' => $_GET['username']);

        try { 
            $stmt = $db->prepare($activationQuery); 
            $result = $stmt->execute($activationQueryParams); 
        } catch(PDOException $ex) {
            die("Failed to run query: " . $ex->getMessage());
        }

        $activationRowCount = $stmt->rowCount();

        if ($activationRowCount) {
            while ($row = $stmt->fetch(PDO::FETCH_ASSOC)){
                $key = $_GET['key'];
                $databaseKey = $row['activationKey'];

                if ($key == $databaseKey) {
                    $updateActivated = "UPDATE users SET activated = 1 WHERE username = :username"; 
                    $updateActivatedParams = array(':username' => $_GET['username']);

                    try { 
                        $stmt = $db->prepare($updateActivated); 
                        $result = $stmt->execute($updateActivatedParams); 
                    } catch(PDOException $ex) {
                        die("Failed to run query: " . $ex->getMessage());
                    }

                    $updateKey = "UPDATE users SET activationKey = '' WHERE username = :username"; 
                    $updateKeyParams = array(':username' => $_GET['username']);

                    try { 
                        $stmt = $db->prepare($updateKey); 
                        $result = $stmt->execute($updateKeyParams); 
                    } catch(PDOException $ex) {
                        die("Failed to run query: " . $ex->getMessage());
                    }

                    echo "Your account has been activated!";

                } else {
                    echo "Sorry, it looks like that activation key doesn't exist!";
                }
            }
        }
    }
?>

现在，这段代码可以正常运行。我遇到的问题是当它通过所有检查并让我回复时：

  

您的帐户已被激活！

当它吐出该消息时，它会终止其下面的所有HTML运行。但是当条件不满足并且它吐出错误回声时，HTML就会很好地呈现而没有任何问题。

我已经多次看了这个，看不到我需要改变的东西，但是，这就是我在这里问的原因。希望它是我错过的一些简单。