Best way of returning differences of two json files programatically

Question

I have two json files and I would like to get a json containing the differences. It is important that only the actual differences of content should be shown, regardless of changing the order of some elements.

What would be the best way to do that? I am searching for a solution as efficient as possible, since jsons may contain lots of data, and users need jobs to be done as quick as possible.

Note: The jsons might contain data encoded at different depths. Any programming language is ok, but I would prefer an answer that could easily be implemented in php.

Answer 1

For this task you can try with https://github.com/swaggest/json-diff

It will do key-wise recursive comparison (order of keys does not matter) and produce JSON Patch (specified in RFC 6902 from the IETF).

Answer 2

Basically, what you want is something similar to array_diff_assoc, but applied to json objects, and recursive.

The array_diff functions are not recursive because of reference issues: it is possible to assign a reference of an array to an entry of that array, making the array infinitely recursive. I don't think it is possible to get the same situation with a json object, thus making a recursive function safe.

Let's suppose that you wish to compute the difference between object A and B, and have the result in object C. The principle is to loop over each field of A (a foreach should do), and when:

• no such field exist in B, copy it over C.
• a similar field exist in B, put in C the result of the difference of A field with B field, which is a recursive call on the diff function with those field as parameter, as well as a fresh object for the result.

The ordering of A should be respected.