Return multiple vars inside loop PHP - php

Question

I want to return multiple notifications within a loop. I have 2 functions, the first one which pulls the notifications from the database and the second one for the dashboard header. The dashboard header is where the notifications will be displayed.
Now, the issue is, for some reason only one notification will be displayed. I've tried changing the return inside the loop to echo but that outputs the notifications at the beginning of dashboardTop().
What's going wrong and how can I resolve this?
public function loopNotifications() {
$stmt = $this->conn->prepare("SELECT * FROM notification WHERE isto=:user_id");
$stmt->execute(array(':user_id'=>$_SESSION['user_id']));
while ($notification = $stmt->fetch(PDO::FETCH_ASSOC)) {
$from = $this->pullName($notification['isto']);
return '<li>' . $notification['content'] . '</li>';
}
}
public function dashboardTop() {
echo '
<div class="collapse navbar-collapse">
<ul class="nav navbar-nav navbar-right">
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">
<i class="material-icons">notifications</i>
<span class="notification">' . $this->notificationCount() . '</span>
<p class="hidden-lg hidden-md">Notifications</p>
</a>
<ul class="dropdown-menu">
' . $this->loopNotifications() . '
</ul>
</li>
<li>
<a href="index.php?page=profile" class="dropdown-toggle" data-toggle="dropdown">
<i class="material-icons">person</i>
<p class="hidden-lg hidden-md">Profile</p>
</a>
</li>
</ul>
</div>
';
}

Answer 1

public function loopNotifications() {
$stmt = $this->conn->prepare("SELECT * FROM notification WHERE isto=:user_id");
$stmt->execute(array(':user_id'=>$_SESSION['user_id']));
$out=''; //empty var tof concaternation
while ($notification = $stmt->fetch(PDO::FETCH_ASSOC)) {
$from = $this->pullName($notification['isto']);
$out.= '<li>' . $notification['content'] . '</li>'; //concaternate each line in to string
}
return $out; //return whole string
}
public function dashboardTop() {
echo '
<div class="collapse navbar-collapse">
<ul class="nav navbar-nav navbar-right">
<li class="dropdown">
<a href="#" class="dropdown-toggle" data-toggle="dropdown">
<i class="material-icons">notifications</i>
<span class="notification">' . $this->notificationCount() . '</span>
<p class="hidden-lg hidden-md">Notifications</p>
</a>
<ul class="dropdown-menu">
' . $this->loopNotifications() . '
</ul>
</li>
<li>
<a href="index.php?page=profile" class="dropdown-toggle" data-toggle="dropdown">
<i class="material-icons">person</i>
<p class="hidden-lg hidden-md">Profile</p>
</a>
</li>
</ul>
</div>
';
}