Collection classes for PHP

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1.4.8 2016-02-01 20:28 UTC


This library is a group of collection classes for PHP. Currently there is one collection complete, aptly called Collection.


A PHP implementation of a templated list. The Collection class allows one object type and its subtypes to be added to the collection. Many standard PHP array functions are encapsulated in the collection.


Requires PHP 5.4 or greater


First, here are example classes used within the Collection examples

  class Book{
    protected $title;
    protected $genre;
    protected $author;

    public function __construct($title, $author, $genre){
      $this->title = $title;
      $this->author = $author;
      $this->genre = $genre;

    public function getTitle(){
      return $this->title;

    public function getAuthor(){
      return $this->author;

    public function getGenre(){
      return $this->genre;

  class Novel extends Book{

  class Novella extends Book{

Basic Usage

There are various ways to add items to the collection, such as appending to the end of the collection or inserting at a specific index

use Collection\Collection;

$library = new Collection("Book");
$library->add(new Novel("1984","George Orwell","Dystopian"));

$items = array();
$items[] = new Novella("Animal Farm","Animal Farm","Satire");
$items[] = new Novel("A Brave New World","Aldous Huxley","Dystopian");

$library->insert(2,new Novel("I, Robot","Isaac Asimov","Science

Elements can be retrieved in various ways. The at method returns the object at your specified index

$book = $library->at(0);

The collection can be fetched as an array

$books = $library->toArray();

Items can be removed with various functions, whether removing at a specified index or matching some callback criteria. The remove method will remove the first item to satisfy the condition. The removeLast method will remove the final match.


  return $book->getGenre() == "Science Fiction";

  return $item->getGenre() == "Dystopian";

Similarly, callbacks can be used to find items or the index of items that satisfy a conditional callback. The find method returns the first result.

$book = $library->find(function($book){
  return $book->getAuthor() == "George Orwell";

$book = $library->findAll(function($book){
  return $book->getGenre() ==  "Dystopian";

$book = $library->findIndex(function($book){
  return $book->getTitle() = "A Brave New World";

The collection can be used in loops

foreach($library as $book){
  echo $book->getTitle();

for($i = 0; $i<$library->count(); $i++){
  echo $library->at($i)->getAuthor();


In the examples above, we see the inheritance support for the Collection. By designating the base class (Book), we can submit Books, Novels and Novellas.


Due to the lack of generics in PHP, we cannot type hint on the collection when it is used as an argument. The simplest way for us to ensurce collection safety is to manually check the object type.

class MyClass
   public function __construct(Collection $collection)
       if ("Book" != $collection->getObjectName()) {
            throw new InvalidArgumentException("Collection must be a collection of Books");



A tuple is an immutable collection where elements are accessible by index.

$t = new Tuple("Apple", "Orange", "Banana");
echo $t[0]; //Apple;


A dictionary is a collection where elements are stored as key/value pairs and only accessible by keys. A dictionary is useful when you intend your array to always use keys and entries may need to be edited or removed.

$d = new Dictionary(array(
    "MI" => "Michigan",
    "OH" => "Ohio"
$d['WI'] = "Wisconsin";
echo $d['MI']; //Michigan

If no keys are provided on construction, indexed keys will be assumed. However, keys will be required for adding additional elements.

$d = new Dictionary(array("Apples", "Bananas"));
echo $d[1]; //Bananas
$d[] = "Oranges" //NullKeyException


An enumeration functions like an immutable dictionary. This collection is useful when keys and values are needed, but no additional keys should be added or removed and no values should be changed. Like a dictionary, indexed keys will be assumed if explicit keys are not provided.

$suits = new Enumeration(array("Spades", "Clubs", "Hearts", "Diamonds"));
echo $suits[1]; //Clubs
$suits[1] = "Bells" //Exception
$suits[4] = "Eagles" //Exception

$colors = new Enumeration(array(
    "Spades" => "Black",
    "Clubs" => "Black",
    "Hearts" => "Red",
    "Diamonds" => "Red"

echo $colors[$suits[0]]; //Black


Thank you to all of the contributors and code reviewers