You need to json encode the data you are sending and set the content-type also:
Change:
$opts = array(
CURLOPT_URL => 'https://zapier.com/hooks/catch/n/abcd',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_CUSTOMREQUEST => 'POST',
CURLOPT_POST => 1,
CURLOPT_POSTFIELDS => 'guid='+ $_POST["guid"] + '&video_title=' + $_POST["video_title"] + '&email=' + $_POST["email"],
);
to:
$data = array('guid' => $_POST["guid"], 'video_title' => $_POST["video_title"], 'email' => $_POST["email"]);
$jsonEncodedData = json_encode($data);
$opts = array(
CURLOPT_URL => 'https://zapier.com/hooks/catch/n/abcd',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_CUSTOMREQUEST => 'POST',
CURLOPT_POST => 1,
CURLOPT_POSTFIELDS => $jsonEncodedData,
CURLOPT_HTTPHEADER => array('Content-Type: application/json','Content-Length: ' . strlen($jsonEncodedData))
);
This should work.