Uncaught exception 'Exception' with message 'Serialization of 'SimpleXMLElement' is not allowed'

You have to cast the XML data to a string because internally they are all SimpleXMLElement

$event['mov'][$y]['name'] = (string)$child->name;
$event['mov'][$y]['movie_id'] = (string)$child->venues->venue->attributes()->id;
$event['mov'][$y]['description'] = (string)$child->description;