This library (or rather module) was inspired by C#s LINQ library.

However, it is not a full-featured LINQ library. It is only a small subset of the functionality since user-land PHP code cannot fully support all the syntactic sugar. For example, the main feature of LINQ, SQL-like syntax directly in source, is not supported since it would require you to compile/transpile your code, which is not in the scope of this library.

The main idea, however, is to provide a way to iterate over a collection of objects in a more natural/handy way like you can do with IEnumerables in C#.

<?php
declare(strict_types=1);

use Elephox\Collection\Enumerable;

$data = [5, 2, 1, 4, 3];
$arr = Enumerable::from($data);

$arr->orderBy(fn (int $item) => $item)
    ->select(function (int $item) {
      echo $item;
    });

// output: 12345


$arr->where(fn (int $item) => $item % 2 === 0)
    ->select(function (int $item) {
        echo $item;
    });

// output: 24

echo $arr->aggregate(fn (int $acc, int $item) => $acc + $item, 0);

// output: 15

• PHP doesn't support generics. For now, only static analyzers like Psalm can provide full type safety when working with generic collections.
• No extension methods from the System.Data namespace are implemented (CopyToDataTable)
• Cast wouldn't make sense in a dynamically typed language, so it is not implemented either. You can use Enumerable::select to change the type of the values.
• GroupJoin is not implemented (yet?)
• Methods ending with OrDefault always has null as the default value. You can, of course, pass your own default value.
• PHP has no default comparer for types, so we provide a DefaultEqualityComparer class that implements some methods to compare two values. Depending on if an order is required, DefaultEqualityComparer::same or DefaultEqualityComparer::compare is used if you don't provide a comparer function yourself.
• LongCount is not implemented since PHP only has one integer type
• OfType is not implemented since PHP doesn't have generics
• ToHashSet, ToDictionary and ToLookup are not implemented. Instead, you can convert an Enumerable to native types via toList and toArray (whereas toArray keeps the keys or allows you to pass a key selector function)
• AsParallel and AsQueryable are not implemented
• None of the System.Xml extension methods are implemented (Ancestors, Descendants, Elements, etc.)
• No read only or immutable interfaces or methods to get them exist (yet?)
• TryGetNonEnumeratedCount is not implemented