HTTP Request

The traditional loading of a page is a http request, e.g. calling the main address https://foodsharing.de calls /index.php which uses other php files to answer the request. The php builds html, css and javascript and sends them to the client.

XHR

XHR is widely used throughout the project but should be replaced. So do not implement new features with XHR!

We use XHR (XMLHttpRequest) for information transferred from the server to the client which is not a complete new page but javascript-initiated. For example, the Update-Übersicht on the Dashboard is loaded by an XHR that gets a json file with the information of the updates. The javascript is found in /client/src/activity.js, it calls addresses like http://foodsharing.de/xhrapp.php?app=basket&m=infobar. This requests an answer by /xhrapp.php which in turn calls the correct php file based on the options that are given after the ? in the url. For example, the activity.js requests are answered by /src/Modules/Activity/ActivityXHR.php. In this case, the database is queried for the information via the ActivityModel.php which in turn uses the /src/Modules/Activity/ActivityGateway.php.

XHR-request answers contain a status and data and ? and always sends the HTTP-status 200. So errors are not recognizable by the HTTP-status but by a status in the sent json data.

nodejs for messages

The chats have a separate way of communication between client and server. For all other pages the initiative starts at the client, the client sends a request to the (php) server and gets an answer. Each request uses one connection that is closed afterwards. This is not useful for the chats since the server knows that there are new messages and has to tell the client.

For this case there exists a separate nodejs server (on the same machine as the php server but separate). This holds an open connection to each user that has foodsharing.de open on their device. Each time a message arrives at the php server, it sends this information to the nodejs server via a websocket which uses the connection to the client to send the message. Note that there can be several connections to each session, of which there can be several for each user. nodejs sends the message to all connections of all addressed users.

The code for the nodejs server is found in /chat/server.js and other files in /chat chat/socket.io -> nodejs server, in chat/server.js. There is documentation for all used parts in /chat/node_modules/<modulename>/Readme.md. All nodejs-documentation is found on their webpage.

REST API

The more modern way to build our api is a REST api by FOS (friends of symfony).

In the Code quality page we have some notes on how to define the REST API Endpoints.

The javascript code that sends REST API requests is found under /client/src/api and is used by other javascript by import.

All php classes working with REST requests are found in /src/Modules/Controllers/<..>RestController.php. This is configured in /config/routes/routing.yml. There it is also configured, that calls to /api/ are interpreted by the REST api, e.g.

https://foodsharing.de/api/conversations/<conversationid>

This is being called when you click on a conversation on the „Alle Nachrichten“ page.

REST is configured via annotations in comments in functions.

• @Rest\Get("subsite") specifies the address to access to start this Action: `https://foodsharing.de/api/subsite"
• @Rest\QueryParam(name="optionname") specifies which options can be used. These are found behind the ? in the url: http://foodsharing.de/api/conversations/687484?messagesLimit=1 only sends one message.
• Both Get and QueryParam can enforce limitations on the sent data with requirement="<some regular expression>".

Functions need to have special names for symfony to use them: the end with Action. They start with a permission check, throw a HttpException(401) if the action is not permitted. Then they somehow react to the request, usually with a Database query via the appropriate Model or Gateway classes.

During running php, the comments get translated to convoluted php code. REST also takes care of the translation from php data structures to json. This json contains data. Errors use the error codes of http-requests.

While reading and writing code a (basic) manual and an annotation overview will help.

Services

In /src/Services we have services.

Sockets

In /src/Sockets, we have sockets. We use them to reduce the use of func.inc.php.