src/CoreBundle/Resources/views/Lti/launch.html.twig
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>LTI Launch</title>
</head>
<body>
<form action="{{ launch_url }}" name="ltiLaunchForm" method="post" encType="application/x-www-form-urlencoded">
{% for key, value in params %}
<input type="hidden" name="{{ key }}" value="{{ value }}">
{% endfor %}
</form>
<script>document.ltiLaunchForm.submit();</script>
</body>
</html>