Example of collection in php. More: http://codely.tv/screencasts/finder-kata-php-colecciones-funcional

someusage.php

<?php

// We want to find all users born after 1950

$users = [new User(1994), new User(2000), new User(1900), new User(25)];

$usersBornedAfter1950 = [];

foreach ($users as $user) {
    if ($user->birthYear() > 1950) {
        $usersBornedAfter1950[] = $user;
    }
}

var_dump($usersBornedAfter1950); // [User(1900), User(25)]

user.php

<?php

// User.php
final class User
{
    private $birthYear;
    
    public function __construct(int $birthYear) 
    {
        $this->birthYear = $birthYear;
    }
    
    public function birthYear(): int
    {
        return $this->birthYear;
    }
}

users-filter.php

<?php

use function Lambdish\Phunctional\filter;

final class Users
{
    private $users;
    
    public function __construct(User ...$users)
    {
        $this->users = $users;
    }
    
    public function bornAfter(int $year): Users
    {        
        return new self(filter($this->hasBornAfter($year), $this->users));
    }
  
    private function hasBornAfter(int $year)
    {
        return function (User $user) use ($year) {
            return $user->birthYear() > $year;
        };
    }  
}

users.php

<?php

final class Users
{
    private $users;
    
    public function __construct(User ...$users)
    {
        $this->users = $users;
    }
    
    public function bornAfter(int $year): Users
    {
        $usersBornedAfterYear = [];

        foreach ($this->users as $user) {
            if ($user->birthYear() > $year) {
                $usersBornedAfterYear[] = $user;
            }
        }
        
        return new self($usersBornedAfterYear);
    }
}