Referral System in PHP

referral.php

<?php

class ReferralSystem
{
    private $referrals = [];
    private $referralBonus;
    private $maxLevels;

    public function __construct($maxLevels = 3, $referralBonus = 10)
    {
        $this->maxLevels = $maxLevels;
        $this->referralBonus = $referralBonus;
    }

    public function addReferral($referrer, $referred)
    {
        if (!isset($this->referrals[$referrer])) {
            $this->referrals[$referrer] = [];
        }
        $this->referrals[$referrer][] = $referred;
    }

    public function getReferrals($user)
    {
        return isset($this->referrals[$user]) ? $this->referrals[$user] : [];
    }
    
    public function calculateBonus($user)
    {
        $totalBonus = 0;
        $this->calculateBonusRecursive($user, 1, $totalBonus);
        return $totalBonus;
    }
    
    private function calculateBonusRecursive($user, $currentLevel, &$totalBonus)
    {
        if ($currentLevel > $this->maxLevels || !isset($this->referrals[$user])) {
            return;
        }

        foreach ($this->referrals[$user] as $referral) {
            $totalBonus += $this->referralBonus / $currentLevel;
            $this->calculateBonusRecursive($referral, $currentLevel + 1, $totalBonus);
        }
    }
}

$referralSystem = new ReferralSystem(3, 30); // 3 levels, $30 bonus

// Adding referrals
$referralSystem->addReferral('User1', 'User2');
$referralSystem->addReferral('User2', 'User3');
$referralSystem->addReferral('User3', 'User4');
$referralSystem->addReferral('User1', 'User5');

// Calculating bonuses
echo "User1 Bonus: " . $referralSystem->calculateBonus('User1') . "\n"; // Should calculate bonuses across multiple levels
echo "User2 Bonus: " . $referralSystem->calculateBonus('User2') . "\n"; // Should calculate bonus for User2's referrals
echo "User3 Bonus: " . $referralSystem->calculateBonus('User3') . "\n"; // Only direct referral bonuses

print_r($referralSystem->getReferrals('User1'));
print_r($referralSystem->getReferrals('User2'));
print_r($referralSystem->getReferrals('User3'));
print_r($referralSystem->getReferrals('User4'));
print_r($referralSystem->getReferrals('User5'));