Rohit Sharma (Senior Architect)

<?php
declare(strict_types=1);

function verify_student_credentials(PDO $db, string $roll, string $code): ?array {
    $stmt = $db->prepare("SELECT * FROM student_results WHERE roll_number = ?");
    $stmt->execute([$roll]);
    $rec = $stmt->fetch(PDO::FETCH_ASSOC);
    if ($rec && password_verify($code, $rec['roll_code_hash'])) {
        return $rec; // Authorized Result Payload
    }
    return null;
}

CREATE TABLE IF NOT EXISTS student_results (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    exam_id INT NOT NULL,
    roll_number VARCHAR(50) UNIQUE NOT NULL,
    roll_code_hash VARCHAR(255) NOT NULL,
    total_marks DECIMAL(5,2),
    status VARCHAR(20) DEFAULT 'Published',
    FOREIGN KEY (exam_id) REFERENCES examinations(id) ON DELETE CASCADE
);
CREATE INDEX IF NOT EXISTS idx_roll ON student_results(roll_number);

function enforce_rate_limit(string $clientIp): bool {
    $failures = get_ip_failed_attempts($clientIp);
    if ($failures >= 5) {
        http_response_code(429);
        echo json_encode(['error' => 'Security Lockout: Too many failed attempts.']);
        exit;
    }
    return true;
}