The Quizzle Android App – PHP Backend + Admob + OneSignal

Introduction

The Quizzle is a popular Android app that allows users to play a trivia game with a twist. It's a fun and engaging way to test your knowledge and compete with friends. In this tutorial, we'll show you how to create a PHP backend for The Quizzle app, integrate AdMob for in-app advertising, and utilize OneSignal for push notifications.

Prerequisites

Before we begin, make sure you have the following:

• A basic understanding of PHP and MySQL
• A computer with a PHP development environment (e.g. XAMPP)
• A MySQL database management system
• Android Studio installed on your computer
• A Google AdMob account
• A OneSignal account

Step 1: Create a PHP Backend

In this step, we'll create a PHP backend for The Quizzle app. We'll create a database to store user information, questions, and scores.

1. Create a new folder for your project and create the following files:
   • config.php: This file will contain database connection settings.
   • database.php: This file will contain database queries.
   • user.php: This file will contain user-related functions.
   • question.php: This file will contain question-related functions.
   • score.php: This file will contain score-related functions.
2. In config.php, add the following code:

   
   <?php
   $db_host = 'your_host';
   $db_username = 'your_username';
   $db_password = 'your_password';
   $db_name = 'your_database';

$conn = new mysqli($db_host, $db_username, $db_password, $db_name);

if ($conn->connect_error) { die("Connection failed: ". $conn->connect_error); } ?>

Replace `your_host`, `your_username`, `your_password`, and `your_database` with your actual database settings.

3. In `database.php`, add the following code:
```php
<?php
require_once 'config.php';

function createDatabase() {
    $sql = "CREATE TABLE IF NOT EXISTS users (
        id INT PRIMARY KEY AUTO_INCREMENT,
        username VARCHAR(255),
        password VARCHAR(255)
    );";

    $sql.= "CREATE TABLE IF NOT EXISTS questions (
        id INT PRIMARY KEY AUTO_INCREMENT,
        question TEXT,
        answer TEXT
    );";

    $sql.= "CREATE TABLE IF NOT EXISTS scores (
        id INT PRIMARY KEY AUTO_INCREMENT,
        user_id INT,
        score INT,
        FOREIGN KEY (user_id) REFERENCES users(id)
    );";

    if ($conn->multi_query($sql)) {
        echo "Database created successfully";
    } else {
        echo "Error creating database: ". $conn->error;
    }
}

function insertUser($username, $password) {
    $sql = "INSERT INTO users (username, password) VALUES ('$username', '$password')";

    if ($conn->query($sql)) {
        echo "User inserted successfully";
    } else {
        echo "Error inserting user: ". $conn->error;
    }
}

function insertQuestion($question, $answer) {
    $sql = "INSERT INTO questions (question, answer) VALUES ('$question', '$answer')";

    if ($conn->query($sql)) {
        echo "Question inserted successfully";
    } else {
        echo "Error inserting question: ". $conn->error;
    }
}

function getScores() {
    $sql = "SELECT * FROM scores ORDER BY score DESC";

    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        while ($row = $result->fetch_assoc()) {
            echo $row['username']. ": ". $row['score']. "<br>";
        }
    } else {
        echo "No scores found";
    }
}
?>

This file contains functions to create the database tables, insert users and questions, and retrieve scores.

1. In user.php, add the following code:

   
   <?php
   require_once 'database.php';

function authenticateUser($username, $password) { $sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";

$result = $conn->query($sql);

if ($result->num_rows > 0) {
    return true;
} else {
    return false;
}

}

function getUserScore($username) { $sql = "SELECT score FROM scores WHERE user_id=(SELECT id FROM users WHERE username='$username')";

$result = $conn->query($sql);

if ($result->num_rows > 0) {
    return $result->fetch_assoc()['score'];
} else {
    return 0;
}

}

function updateScore($username, $score) { $sql = "UPDATE scores SET score=$score WHERE user_id=(SELECT id FROM users WHERE username='$username')";

if ($conn->query($sql)) {
    echo "Score updated successfully";
} else {
    echo "Error updating score: ". $conn->error;
}

} ?>

This file contains functions to authenticate users, retrieve user scores, and update scores.

5. In `question.php`, add the following code:
```php
<?php
require_once 'database.php';

function getQuestion() {
    $sql = "SELECT * FROM questions ORDER BY RAND() LIMIT 1";

    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        return $result->fetch_assoc();
    } else {
        return false;
    }
}

function checkAnswer($question_id, $user_answer) {
    $sql = "SELECT answer FROM questions WHERE id=$question_id";

    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        $correct_answer = $result->fetch_assoc()['answer'];

        if ($user_answer == $correct_answer) {
            return true;
        } else {
            return false;
        }
    } else {
        return false;
    }
}
?>

This file contains functions to retrieve a random question and check user answers.

1. In score.php, add the following code:

   
   <?php
   require_once 'database.php';

function updateScore() { $sql = "INSERT INTO scores (user_id, score) VALUES ((SELECT id FROM users WHERE username='$_SESSION[username]'), 0)";

if ($conn->query($sql)) {
    echo "Score updated successfully";
} else {
    echo "Error updating score: ". $conn->error;
}

} ?>

This file contains a function to update the user's score.

**Step 2: Integrate AdMob**

In this step, we'll integrate AdMob into our PHP backend to display ads.

1. Create a new file called `admob.php` and add the following code:
```php
<?php
require_once 'config.php';

function showAd() {
    $ad_unit_id = 'your_ad_unit_id';

    $sql = "SELECT * FROM users WHERE id=(SELECT id FROM users WHERE username='$_SESSION[username]')";

    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        $user_id = $result->fetch_assoc()['id'];

        $ad_request = array(
            'ad_unit_id' => $ad_unit_id,
            'user_id' => $user_id
        );

        $ad_response = json_decode(admob_request($ad_request), true);

        if ($ad_response['status'] == 'OK') {
            echo '<div id="admob-ad"></div>';
            echo '<script>admob.requestAd(admob.adUnitId, {"mediaviewport": true}, function(ad) {document.getElementById("admob-ad").innerHTML = ad;});</script>';
        } else {
            echo 'Error displaying ad: '. $ad_response['error'];
        }
    } else {
        echo 'Error displaying ad: User not found';
    }
}

function admob_request($ad_request) {
    // Replace with your AdMob API key
    $api_key = 'your_api_key';

    $url = 'https://android.clients.google.com/serve/afm/'; // AdMob API URL

    $headers = array(
        'Content-Type: application/json',
        'Content-Length: '. strlen(json_encode($ad_request))
    );

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($ad_request));
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

    $response = curl_exec($ch);
    curl_close($ch);

    return $response;
}
?>

Replace your_ad_unit_id and your_api_key with your actual AdMob settings.

1. In index.php, add the following code:

   
   <?php
   require_once 'admob.php';

if (isset($_SESSION['username'])) { showAd(); } ?>

This will display the AdMob ad on the index page.

**Step 3: Integrate OneSignal**

In this step, we'll integrate OneSignal into our PHP backend to send push notifications.

1. Create a new file called `onesignal.php` and add the following code:
```php
<?php
require_once 'config.php';

function sendPushNotification($message, $users) {
    $onesignal_app_id = 'your_onesignal_app_id';
    $onesignal_api_key = 'your_onesignal_api_key';

    $headers = array(
        'Content-Type: application/json',
        'Authorization: Basic '. base64_encode($onesignal_app_id. ':'. $onesignal_api_key)
    );

    $url = 'https://onesignal.com/api/v1/notifications';

    $data = array(
        'app_id' => $onesignal_app_id,
        'contents' => array(
            'en' => $message
        ),
        'included_segments' => array(
            'All'
        ),
        'filters' => array(
            array(
                'field' => 'user_id',
                'key' => 'equals',
                'relation' => '=',
                'value' => $users
            )
        )
    );

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

    $response = curl_exec($ch);
    curl_close($ch);

    return $response;
}
?>

Replace your_onesignal_app_id and your_onesignal_api_key with your actual OneSignal settings.

1. In index.php, add the following code:

   
   <?php
   require_once 'onesignal.php';

if (isset($_SESSION['username'])) { $users = array($_SESSION['username']); sendPushNotification('Hello!', $users); } ?>

This will send a push notification to the user when they log in.

**Conclusion**

In this tutorial, we've created a PHP backend for The Quizzle app, integrated AdMob for in-app advertising, and utilized OneSignal for push notifications. We've also covered the basics of creating a database, inserting users and questions, and retrieving scores. With this tutorial, you should be able to create a fully functional Android app with a PHP backend.