Howto: PHP/Javascript communication

Question

As I'm developing my WebIDE, I keep coming up with questions that I cannot answer myself. This is because the project is supposed to help others create what they would "normally" create, but faster (i.e. as automated as possible). In this light, my question is how to you implement a PHP backend?

Here is what I do. I like to create "functions" that the client JavaScript can call. Usually, I send (via POST and JSON) a variable called "action" which holds the name of the "function" I am calling (as well as any arguments I wish to send it). The PHP code, then, looks something like this:

if(issset($_POST['action'])) {
    //function foo(arg1,arg2)
    if($_POST['action'] == 'foo') {
        $arg1 = $_POST['arg1'];
        $arg2 = $_POST['arg2'];
        //do stuff
    }
}

I can still reference other real functions I create in PHP, but I find that this is a nice way to organize everything and easy to implement in both JavaScript and PHP.

What do you do?

Edit 1: Ok, based on the first two answers to this question, I do not think I am explaining myself well.

I am asking how do you create a PHP back end. The idea is that you have your AJAX client written in JavaScript (or maybe something else, it doesn't matter), and then it will call your backend PHP with POST or GET data. Based on this data, your backend will do what it needs to do (maybe it will simply update the database, and maybe even return information, again: it doesn't matter).

The question now is: how do you tell it what to do? What do you send via POST/GET and how do you interpret it in your backend?

Answer 1

I do something very similar. What you need is a JSON object to pass back to the javascript. When you are done with your PHP, you can call json_encode to pass an object back to the front end. From there you can do more with it in Javascript or format it however you want.

There is more information on a similar question here: http://stackoverflow.com/questions/393479/best-way-to-transfer-an-array-between-php-and-javascript/393497#393497

Edit: After reading your edit, I think what you are doing is fine. When you send the AJAX request from Javascript include a variable like "action", or whatever youd like. From there you can check what the action is via a case and switch statement.

Answer 2

I usually write the php functions as normal functions.

fn1(arg1, arg2){
 //do stuff here
}
fn2(arg3){
 //do stuff here
}

I pass the name of the function in a variable called action. Then do this:

foreach($_POST as $key => $value) 
$$key = $value;

To assign create variables of the same name as the arguments.

Then use a switch-case to call the appropriate function like so:

switch($action){
 case 'fn1':fn1(arg1,arg2);
 break;
 case 'fn2':fn2(arg3);
 break;
}

Is this what you are looking for?

Edit: You could use the PHP SOAP and XML-RPC extension to develop a webservice, where if you specify the function name in the SOAP request, that function will be automatically executed (you don't have to write the switch-case or if). I've used it in Java, but am not sure how exactly it works in PHP.

Answer 3

The question now is: how do you tell it what to do? What do you send via POST/GET and how do you interpret it in your backend?

Choose your own conventions. For example use an "action" value in your JSON data that tells the action, then add more parameters. You can spy on various websites's Ajax messages with Firebug extension in Firefox if you want to see what other websites do.

For example the Json POST data could be:

{
    action: "create",
    fields: {
       firstname: "John",
       lastname: "Doe",
       age: 32
    }
}

To which you could reply with the ID of the newly created record.

To delete the record:

{
    action: "delete",
    keys: {
        id: 4654564
    }
}

etc.

In the php ajax handler you could have something as simple as a switch:

$jsonData = Services_Json::decode($_POST['json']);
switch ($jsonData->action)
{
    case "save":
        if (validate_json_data($jsonData->fields))
        {
            UsersPeer::create($jsonData->fields);
        }
        break;
    case "delete":
        /* etc */
}

// return a json reply with 
$jsonReply = new stdClass;
$jsonReply->status = "ok";
$jsonReply->statusMessage = "Record succesfully created";
echo Services_Json::encode($jsonReply);
exit;

Javascript, say prototype Ajax.Request responder function will output the error message in a specially created DIV if "status" is not "ok", etc...