Array Of Class Objects

A class may have a member that is array and contains class instances.

Example

<?php
class Car {
    private $model;
    private $price;

public function __construct($model, $price) {
        $this->model = $model;
        $this->price = $price;
    }

public function printData() {
        echo "Model: " . $this->model . "\n";
        echo "Price: " . $this->price . "\n";
    }

public function getPrice() {
        return $this->price;
    }
}

class CarDealership {
    public $cars = [];

public function sortByPrice() {
        // sort cars by price:
        usort($this->cars, function ($a, $b) {
            if($a->getPrice() < $b->getPrice()) {
                return -1;
            }
            else if ($a->getPrice() === $b->getPrice()) {
                return 0;
            }

return 1;
        });
    }
}

$carDealership = new CarDealership();

$car_1 = new Car("Ford Fiesta", 20000);
$car_2 = new Car("Toyota Corolla", 26000);
$car_3 = new Car("Renault Clio", 18000);

// Add elements to the array:
$carDealership->cars[] = $car_1;
$carDealership->cars[] = $car_2;
$carDealership->cars[] = $car_3;

echo "Before Sorting: \n \n";

foreach ($carDealership->cars as $car) {
    echo "--------\n";
    $car->printData();
}

$carDealership->sortByPrice();
echo "\n \nAfter Sorting: \n \n";

foreach ($carDealership->cars as $car) {
    echo "--------\n";
    $car->printData();
}

Output:

Explanation:

At line 22 an empty array is declared.
At lines 46 - 48 elements are added to the array. This can be done also via the function array_push.
At lines 52 and 60 all elements of the array are looped.
At lines 26 - 35 the array is sorted ascending by price. If at line 27 the sign < is replaced with >, then the sorting would be descending.