WebDev Novice: How should I approach passing a complex object from PHP to PHP (non-contiguous)

Question

So, I'm originally a native application developer (mostly C++), but I've found myself working on a small business Coding project for a friend. I'm used to self contained native applications and I'm struggling with a current problem on my project:

I have an AppInstance class in PHP which is implemented as a singleton (I've heard that most of the time this isn't really the best way to do things, and I concede this). This class contains a few basic operating parameters for the application (mostly simple strings and numbers), as well as an array of complex objects (objects composed of other objects, arrays and other members and methods). I'd like to be able to pass any/all of this application data between this original PHP script (which initializes all of the values that my program needs to run, and outputs the default HTML of my UI).

I then begin to handle user input actions with Javascript. Some of these inputs require information from the original PHP script. Because the processing of these inputs requires a bit more computation, I'd like to use AJAX to call this processing on the server (in PHP) and return the output. However, Because this processing requires some of the objects from the original PHP script, I'm trying to figure out how I should pass these objects around in the most efficient way?

I've read that I can use JSON encode to effectively serialize my objects and send them to JS (the UI in this case), and these objects can be returned to PHP ( see this ). But my question really is a multi-part:

1. Would it be more efficient to perform all calculations and processing on the server (in PHP, rather than doing it all on the client-side in JS)?
2. If the answer to #1 is "Yes", my first inclination is to serialize the PHP object to a file on the server, and have the new PHP script read and deserialize the object. Is there a more efficient method than this and,if not, should I serialize in JSON or PHP's serialize() format?

Edit: I should probably mention that some of my objects also possess resource variable, as I know this has some effect on serialization.

Answer 1

In terms of efficiency I would be looking at whatever reduces the number of network (AJAX) calls, as this will usually be your largest overhead. This is hard to comment on in your case because I don't know how often a client is going to be making such calls. A bigger worry for me is security, as Javascript would be able to manipulate values it gets from the AppInstance. I personally would consider an API which only exposes actions you permit.