Amazon ALEXA Lists Exercise – Put’em on Paper…

4.3 Edge server PHP code

Your EDGE server must be able to run PHP code. I have a LAMP running latest PHP 7.0 and this tiny exercise script named edge_script_printer.php fits perfectly.

• Server is exposed at my dyndns via HOSTNAME:443 with a self signed certificate.
• Script is therefore available at https://$DYNDNSHOST$/edge_script_printer.php . Obviously, if you put this into another path, adapt the python glue code above.
• Script has the following GET or POST parameters:
  • secret : same as above in Python script
  • listName : UTF8 URL encoded name for the list, 1-32 characters
  • listItems : URL encoded JSON list of items, e.g. [„tomatoes“, „mozarella“] becomes %5B%22tomatoes%22%2C%20%22mozarella%22%5D%C2%A0 . Note that on older PHP5 json implementations you cannot use an apostroph, but must use double quotes as shown here.

Aaaand here’s the EDGE server code, nothing fancy:

<?php
	// small obscurity secret checking...
	$localsecret = "1234567890__REPLACE__WITH__YOUR__SECRET__1234567890" // obviously, same as above in python script
	$secret = $_REQUEST["secret"];
	if ($localsecret != $secret) {
		header("HTTP/1.1 403 Unauthorized");
		exit(1);
	}
	$listName  = urlencode($_REQUEST["listName"]);
	$listItems = json_decode($_REQUEST["listItems"]);
	// Remove comment to test and track issues
	// ob_flush();
	// ob_start();
	// var_dump($_REQUEST["listName"]);
	// var_dump($_REQUEST["listItems"]);
	// file_put_contents("edge_script_printer_dump.txt", ob_get_flush()."\r\n", FILE_APPEND);		
	if (!is_array($listItems) || count($listItems)<1 || count($listItems)>30) {
		header("HTTP/1.1 400 Bad Request");
		$error = array(
			"statusCode"=>400,
			"statusText"=>"Please provide at least 1 and at best 30 list item(s) in request parameter named 'listItems' in form of a JSON UTF8 list.",
			"listName"=>$_REQUEST["listName"],
			"listItems"=>$_REQUEST["listItems"]
		);
		echo json_encode($error);
		exit(2);
	}
	$ch = curl_init("http://!!!!!!!!!INTERNAL_PRINT_SERVER_HOST_NAME_OR_IP!!!!!!!!!/internal_printer.php?listName=$listName&listItems=". urlencode($_REQUEST["listItems"]));
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
	curl_setopt($ch, CURLOPT_HEADER, 0);
	curl_setopt($ch, CURLOPT_TIMEOUT, 3);
	$data = curl_exec($ch);
	$code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
	if ($code != 200) {
		header("HTTP/1.1 500 Internal Server Error");
		exit(1);
	}
	curl_close($ch);	
	header("HTTP/1.1 200 OK");
	echo "List printed successfully.";
?>

Note that you’re required to change two things:

1. line 3: use your own secret here from above (python script).
2. line 28: replace with your raspberry pis internal, static IP address or host name.

The script just passes on listName  and listItems  as-is to the internal print server and waits for a reply.

4.4 Testing

As an intermediate step, we can test at this point by uncommenting the five lines in the PHP script above.

• Tell ALEXA to put tomatoes on your shopping list
• Ask ALEXA to start „list printer“, this should result in a listName=“shopping list“  and listItems=[„tomatoes“]  dumped to the edge_script_printer_dump.txt  file.

You can use Amazon CloudWatch to track any errors in the Python Script.