Digantara Backend Developer Assignment

Overview

This project is designed to demonstrate proficiency in backend development, algorithm implementation, and API design. It includes three RESTful APIs implemented in PHP using XAMPP and MySQL. Each API executes a fundamental data structure algorithm and logs all requests in a MySQL database for tracking and persistence. The implemented algorithms are:

• Binary Search: Efficiently searches for an element in a sorted array.
• Quick Sort: Sorts an array using the divide-and-conquer strategy.
• Breadth-First Search (BFS): Traverses a graph structure level by level.

These APIs are designed to handle input validation, error responses, and structured logging to ensure a robust and efficient backend system.

Technologies Used

This project leverages the following technologies to implement and deploy the backend solution:

• PHP: The core programming language used to implement API logic.
• XAMPP: A local server environment that includes Apache, MySQL, and PHP.
• MySQL: A relational database used for storing API logs, including input and output data.
• Postman: A tool for testing API requests and responses.

Database Setup

To ensure proper logging of API requests, set up a MySQL database by following these steps:

1. Open the XAMPP Control Panel and start Apache and MySQL.
2. Open phpMyAdmin and create a new database named test.
3. Run the following SQL command to create a table for storing API call logs:

   CREATE TABLE db_algo (
       id INT AUTO_INCREMENT PRIMARY KEY,
       algorithm VARCHAR(100),
       input VARCHAR(100),
       output VARCHAR(100),
   );

   This table will automatically record each API call, storing details about the algorithm used, input provided, output generated, and the timestamp of execution. For convenience purpose I have provided db_algo.sql file for the setup of the table.

Installation and Setup

To set up the project locally, follow these steps:

1. Download and install XAMPP from Apache Friends.
2. Copy the PHP API files (binary_search.php, quick_sort.php, and bfs.php) into the htdocs directory of your XAMPP installation.
3. Start the XAMPP Control Panel and ensure both Apache and MySQL services are running.
4. Open a browser and go to http://localhost/phpmyadmin/ to verify the database setup.
5. Use Postman or cURL to test API endpoints by sending POST requests with the required JSON payloads.

API Endpoints

Each algorithm has a dedicated API endpoint that receives input in JSON format and returns a structured JSON response. All API calls are logged in the database.

1. Binary Search API

This API performs a binary search on a sorted array and returns the index of the searched element if found.

• Endpoint: /binary_search.php eg.[(http://localhost:8080/learn/project/bs1.php)]
• Method: POST
• Request Body (JSON Format):

  {
      "arr": [2, 4, 6, 8, 10],
      "value": 6
  }

• Response Example:

  {
      "status": "success",
      "algorithm": "Binary Search",
      "input": [2, 4, 6, 8, 10],
      "output": "6 Exists at index 2"
  }

2. Quick Sort API

This API sorts an array using the Quick Sort algorithm and returns the sorted output.

• Endpoint: /quick_sort.php eg.[(http://localhost:8080/learn/project/qs1.php)]
• Method: POST
• Request Body (JSON Format):

  {
      "arr": [9, 4, 7, 3, 1]
  }

• Response Example:

  {
      "status": "success",
      "algorithm": "Quick Sort",
      "input": [9, 4, 7, 3, 1],
      "output": [1, 3, 4, 7, 9]
  }

3. Breadth-First Search (BFS) API

This API performs a BFS traversal on a graph and returns the visited nodes in order.

• Endpoint: /bfs.php eg.[(http://localhost:8080/learn/project/bfs.php)]
• Method: POST
• Request Body (JSON Format):

  {
      "start": "A",
      "graph": {
          "A": ["B", "C"],
          "B": ["A", "D", "E"],
          "C": ["A", "F"],
          "D": ["B"],
          "E": ["B", "F"],
          "F": ["C", "E"]
      }
  }

• Response Example:

  {
      "status": "success",
      "algorithm": "BFS",
      "input": {
          "A": ["B", "C"],
          "B": ["A", "D", "E"],
          "C": ["A", "F"],
          "D": ["B"],
          "E": ["B", "F"],
          "F": ["C", "E"]
      },
      "output": [["A", "B", "C", "D", "E", "F"]]
  }

Accessing Logs

To review API call logs stored in the database, execute the following SQL query in phpMyAdmin or a MySQL terminal:

SELECT * FROM db_algo;

This will display all logged API requests along with their inputs, outputs, and timestamps.

Error Handling

The APIs include robust error handling mechanisms to manage various types of failures:

• Invalid request method (405 Method Not Allowed) – Ensures only POST requests are accepted.
• Missing or incorrect input data (400 Bad Request) – Returns an error if required parameters are missing or incorrectly formatted.
• Database connection failure (500 Internal Server Error) – Handles cases where the database is unreachable or misconfigured.
• Edge cases – Handles cases such as empty arrays, self-loops in BFS, and unsorted arrays in Binary Search.

Optional Enhancements

This project can be extended in several ways to improve performance, usability, and deployment flexibility:

• Deployment: The APIs can be hosted on a cloud-based PHP server such as AWS, DigitalOcean, or Heroku.
• Dockerization: The application can be containerized using Docker for streamlined deployment and scalability.
• Authentication: Implementing API keys or JWT authentication can enhance security.
• Rate Limiting: Prevent abuse by limiting the number of API requests per minute.

Author

This project was developed as part of the Digantara Backend Developer Assignment 2025. It showcases proficiency in backend API development, data structure implementation, and MySQL integration.