POO exercise about classes

Bicycle.php

<?php

class Bicycle
{
    private $color;

    private $currentSpeed;

    private $name;

    private $nbSeats;

    private $nbWheels;

    public function __construct(string $name, string $color)
    {
        $this->color = $color;
        $this->name = $name;
        $this->currentSpeed = 0;
    }

    public function forward()
    {
        $this->currentSpeed = 15;
        return "Go !";
    }


    public function brake(): string
    {
        $sentence = "";
        while ($this->currentSpeed > 0) {
            $this->currentSpeed--;
            $sentence .= "Brake !!!";
        }

        $sentence .= "I'm stopped !";
        return $sentence;
    }

    public function getColor(): string
    {
        return $this->color;
    }

    public function getName(): string
    {
        return $this->name;
    }

    public function getCurrentSpeed(): int
    {
        return $this->currentSpeed;
    }

    public function setCurrentSpeed(int $currentSpeed): void
    {
        if ($currentSpeed >= 0) {
            $this->currentSpeed = $currentSpeed;
        }
    }
}

Car.php

<?php

class Car
{
    private string $brandName;

    private int $nbWheels;

    private int $currentSpeed;

    private string $color;

    private int $nbSeats;

    private string $energyType;

    private int $energyLevel;


    public function __construct(string $brandName, string $color, int $nbSeats, string $energy)
    {
        $this->currentSpeed= 0;
        $this->brandName = $brandName;
        $this->color = $color;
        $this->nbSeats = $nbSeats;
        $this->energy = $energy;
    }

    public function forward()
    {
        $this->currentSpeed++;
    }

    public function brake()
    {
        $this->currentSpeed--;
    }

    public function start() : Car
    {
        $this->currentSpeed = 15;
        return $this;
    }

    public function getNbWheels()
    {
        return $this->nbWheels;
    }

    public function getCurrentSpeed()
    {
        return $this->currentSpeed;
    }

    public function getColor()
    {
        return $this->color;
    }

    public function getNbSeats()
    {
        return $this->nbSeats;
    }

    public function getEnergy()
    {
        return $this->energy;
    }

    public function getEnergyLevel()
    {
        return $this->energyLevel;
    }

    /**
     * Get the value of brandName
     *
     * @return  string
     */
    public function getBrandName()
    {
        return $this->brandName;
    }

    /**
     * Set the value of brandName
     *
     * @param  string  $brandName
     *
     * @return  self
     */
    public function setBrandName(string $brandName)
    {
        $this->brandName = $brandName;

        return $this;
    }
}

index.php

<?php

require_once '../src/Car.php';
require_once '../src/Bicycle.php';

$ford = new Car('Ford', 'blue', 4, 'ethanol');
$mini = new Car('Mini', 'red', 4, 'electric');
$rover = new Car('Rover', 'green', 6, 'gas');
$tesla = new Car('Tesla', 'yellow', 2, 'electric');
$firstBicycle = new Bicycle('rockrider', 'orange');
$secondBicycle = new Bicycle('b-tween', 'black');

echo " Le véhicule " . $ford->getBrandName() . " de couleur " . $ford->getColor() . " avance à une allure de ";
echo "</br>";
$ford->start();
echo $ford->getCurrentSpeed();
echo " | ";

while ($ford->getCurrentSpeed() < 50) {
    $ford->forward();
    echo $ford->getCurrentSpeed();
    echo " | ";
}
echo " <strong> Mega speed nitrooo </strong> ";

echo "</br>";

echo " <strong> Ca suffit les conneries, c'est l'heure de freiner </strong> ";
while ($ford->getCurrentSpeed() > 0) {
    $ford->brake();
    echo $ford->getCurrentSpeed();
    echo " | ";
}

echo "</br>";

echo " Le vélo " . $firstBicycle->getName() . " de couleur " . $firstBicycle->getColor() . " avance à une allure de ";
echo "</br>";
echo $firstBicycle->getCurrentSpeed();
echo " | ";


echo $firstBicycle->forward();
echo $firstBicycle->getCurrentSpeed();

echo " | ";

echo " <strong> Mega roue arrière!</strong> ";

echo "</br>";

echo $firstBicycle->brake();