Collection is a functional utility library for PHP greater than 7.1.3.

It’s similar to other available collection libraries based on regular PHP arrays, but with a lazy mechanism under the hood that strives to do as little work as possible while being as flexible as possible.

Functions like array_map(), array_filter() and array_reduce() are great, but they create new arrays and everything is eagerly done before going to the next step. Lazy collection leverages PHP’s generators, iterators and yield statements to allow you to work with very large data sets while keeping memory usage as low as possible.

For example, imagine your application needs to process a multi-gigabyte log file while taking advantage of this library’s methods to parse the logs. Instead of reading the entire file into memory at once, this library may be used to keep only a small part of the file in memory at a given time.

On top of this, this library:

Except a few methods, most methods are pure and return a new Collection object.

Also, unlike regular PHP arrays where keys must be either of type int or string, this collection library let you use any kind of type for keys: integer, string, objects, arrays, … anything! This library could be a valid replacement for SplObjectStorage but with much more features. This way of working opens up new perspectives and another way of handling data, in a more functional way.

And last but not least, collection keys are preserved throughout most operations, and it might be leading to some confusions, carefully read this example for the full explanation.

This library has been inspired by: