PHP Terminating HTML After Success, Not Error - php

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!";
}
}
}
}
?>
Right now, this code works as it's suppose to. The problem I'm having is when it passes all checks and gives me back the echo:
Your account has been activated!
When it spit's out that message, it terminates all HTML below it from running. But when the conditions are not met and it spits out the error echo, the HTML is rendered just fine with no issues.
I have looked this over soo many times and can't see anything that I need to change, but, that's why I'm asking here. Hopefully it's something simple I missed.