Adding a Value to Collection Items

I want to load data from many files. Each file is named with a date and I need to inject this date to each of the fetched Entries of my file. I know I could do this with an foreach - loop before inserting the data into the collection, but I think there should be a better solution.

Content of one file

[{"price":"95,34","isin":"FR0000120073"},{"price":"113,475","isin":"CA13645T1003"}]

The Code I use to move the data into a collection.

$collection= collect(json_decode(File::get($file)));

I tried for example the "map" method, however I don't know how to pass an additional variable to the anonymous function.

The content of my collection should look like this:

[{"price":"95,34","isin":"FR0000120073","date":"2016-06-23"},{"price":"113,475","isin":"CA13645T1003","date":"2016-06-23"}]

Is there any simple solution using the collections or do I have to use a foreach-loop?

via Chebli Mohamed