HNG-2025 Readme for Stage 1

Setting Up PHP 8.0 with Apache on Ubuntu

Prerequisites

Ensure you have a fresh Ubuntu installation with sudo privileges.

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Step 1: Update System Packages

Before installing new software, update your system packages:

sudo apt update && sudo apt upgrade -y

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Step 2: Install Necessary Packages

Install essential utilities like unzip and p7zip:

sudo apt-get install unzip -y
sudo apt-get install p7zip -y

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Step 3: Install Apache Web Server

Install the Apache web server:

sudo apt install apache2 -y

Ensure Apache is running:

sudo systemctl status apache2

If Apache is not running, start it:

sudo systemctl start apache2

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Step 4: Install PHP 8.0

First, add the ondrej/php repository, which provides multiple PHP versions:

sudo add-apt-repository -y ppa:ondrej/php
sudo apt update

Now, install PHP 8.0:

sudo apt install php8.0 -y

Verify the installation:

php -v

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Step 5: Install PHP Extensions

Install necessary PHP extensions required for the project:

sudo apt install php8.0-dom php8.0-gd php8.0-intl php8.0-mbstring php8.0-xml php8.0-xsl php8.0-zip -y
sudo apt-get install php8.0-curl php8.0-pdo-mysql php8.0-bcmath -y

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Step 6: Set Up API Directory

Navigate to the web root directory and create an /api directory:

cd /var/www/html/
sudo mkdir /api
cd /api

Create the number_classify.php file:

sudo nano number_classify.php

Add the following sample code to classify-number.php:

paste the number_classify.php code inside

Save the file (CTRL + X, then Y, then ENTER).

Test the API by visiting:

http://34.228.212.209/api/number_classify.php?number=371

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Step 7: Configure Apache

Navigate to the Apache configuration directory:

cd /etc/apache2/sites-available/

Remove the default Apache configuration file:

sudo rm 000-default.conf

Create a new 000-default.conf file:

sudo nano 000-default.conf

Add the following configuration:

<VirtualHost *:80>
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html
    <Directory /var/www/html/>
        AllowOverride All
        Require all granted
        Options Indexes FollowSymLinks
    </Directory>
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

Save the file (CTRL + X, then Y, then ENTER).

Restart Apache to apply changes:

sudo systemctl restart apache2

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Understanding number_classify.php

This script processes a given number and classifies it based on specific properties such as being prime, perfect, Armstrong, even, or odd. Below is an explanation of its components:

1. Headers for CORS and JSON Response:

   header("Access-Control-Allow-Origin: *");
   header("Content-Type: application/json");

   These lines ensure that the API can be accessed from any domain and that the response is in JSON format.

2. Prime Number Check:

   function is_prime($n) {
       if ($n <= 1) return false;
       for ($i = 2; $i <= sqrt($n); $i++) 
           if ($n % $i == 0) return false;
       return true;
   }

   This function checks whether a number is prime by iterating up to its square root.

3. Perfect Number Check:

   function is_perfect($n) {
       if ($n <= 1) return false;
       $sum = 1;
       for ($i = 2; $i <= sqrt($n); $i++) 
           if ($n % $i == 0) $sum += $i + ($n / $i);
       return $sum == $n;
   }

   This function determines if a number is perfect by summing its divisors.

4. Armstrong Number Check:

   function is_armstrong($n) {
       $num = abs($n);
       $digits = str_split((string)$num);
       $power = count($digits);
       $sum = array_sum(array_map(fn($d) => pow($d, $power), $digits));
       return $sum == $num;
   }

   An Armstrong number is one where the sum of its digits, each raised to the power of the number of digits, equals the original number.

5. Processing User Input:

   $input = $_GET['number'] ?? null;

   The script retrieves the number parameter from the URL.

6. Validating Input:

   if (!is_numeric($input) || !ctype_digit((string)abs($input))) {
       http_response_code(400);
       echo json_encode(["number" => $input, "error" => true]);
       exit;
   }

   Ensures that the provided input is a valid number.

7. Determining Properties:

   $properties = [];
   if (is_armstrong($number)) { ... }
   elseif (is_prime($abs_num)) { ... }
   elseif (is_perfect($abs_num)) { ... }
   $properties[] = ($abs_num % 2 == 0) ? "even" : "odd";

   Classifies the number based on its properties.

8. Returning the Response:

   echo json_encode([...]);

   The results are returned as a structured JSON response.

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Conclusion

You have successfully set up an Apache server with PHP 8.0 and implemented a number classification API. Test the setup using the provided API endpoint.

For troubleshooting, check Apache logs:

sudo tail -f /var/log/apache2/error.log

When uploading, use:

http://34.228.212.209/api/number_classify.php?number=371# without parameter

Repository: GitHub