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Prerequisites

Before installing Simple Invoice, ensure you have:
  • PHP 5.3.7 or higher
  • MySQL 5.6 or higher
  • Web server (Apache, Nginx, or IIS with PHP support)
  • phpMyAdmin (recommended for database management)

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Installation Methods

Choose the installation method that best fits your environment:
Recommended for local development on Windows

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Windows Installation (XAMPP)

The easiest way to run Simple Invoice on Windows is using XAMPP.
1

Download Source Files

Download the Simple Invoice source files from the repository and extract them.
2

Copy to XAMPP Directory

Copy and extract the files to C:\xampp\htdocs\. You should have a folder called simple_invoice.
C:\xampp\htdocs\simple_invoice\
The application will be accessible at: http://localhost/simple_invoice/
3

Start XAMPP Services

Open XAMPP Control Panel and start:
  • Apache (web server)
  • MySQL (database server)
Ensure both services show green “Running” status before proceeding.
4

Create Database

Access phpMyAdmin at http://localhost/phpmyadmin/ and create a new database:
  1. Click on “New” in the left sidebar
  2. Enter database name: simple_invoice
  3. Select collation: utf8_general_ci
  4. Click “Create”
5

Import Database Tables

Import the database schema:
  1. Select the simple_invoice database
  2. Click on the “Import” tab
  3. Click “Choose File” and select simple_invoice.sql from the root directory
  4. Click “Go” to import
The SQL file is located at: simple_invoice/simple_invoice.sql
6

Configure Database Connection

Edit the database configuration file at simple_invoice/config/db.php:
<?php
/*Datos de conexion a la base de datos*/
define('DB_HOST', 'localhost');  // Usually "127.0.0.1" or "localhost"
define('DB_USER', 'root');       // Your database username
define('DB_PASS', '');           // Your database password
define('DB_NAME', 'simple_invoice'); // Database name
?>
For XAMPP default installation, the settings above should work without changes.
7

Access the Application

Open your web browser and navigate to:
http://localhost/simple_invoice/
You should see the login page.

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Linux Installation (Apache)

For production deployment on Linux servers with Apache.
1

Install Required Packages

Install Apache, PHP, and MySQL:
# Ubuntu/Debian
sudo apt update
sudo apt install apache2 php php-mysql mysql-server
sudo apt install php-mbstring php-xml php-gd

# CentOS/RHEL
sudo yum install httpd php php-mysql mariadb-server
sudo yum install php-mbstring php-xml php-gd
2

Copy Application Files

Copy Simple Invoice to your web root:
sudo cp -r simple_invoice /var/www/html/
sudo chown -R www-data:www-data /var/www/html/simple_invoice
sudo chmod -R 755 /var/www/html/simple_invoice
3

Create MySQL Database

Log into MySQL and create the database:
sudo mysql -u root -p

CREATE DATABASE simple_invoice CHARACTER SET utf8 COLLATE utf8_general_ci;
CREATE USER 'invoiceuser'@'localhost' IDENTIFIED BY 'your_password';
GRANT ALL PRIVILEGES ON simple_invoice.* TO 'invoiceuser'@'localhost';
FLUSH PRIVILEGES;
EXIT;
4

Import Database Schema

Import the SQL file:
mysql -u invoiceuser -p simple_invoice < /var/www/html/simple_invoice/simple_invoice.sql
5

Configure Database Connection

Edit /var/www/html/simple_invoice/config/db.php:
<?php
define('DB_HOST', 'localhost');
define('DB_USER', 'invoiceuser');
define('DB_PASS', 'your_password');
define('DB_NAME', 'simple_invoice');
?>
6

Configure Apache

Create a virtual host (optional but recommended):
<VirtualHost *:80>
    ServerName invoice.yourdomain.com
    DocumentRoot /var/www/html/simple_invoice
    
    <Directory /var/www/html/simple_invoice>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
    
    ErrorLog ${APACHE_LOG_DIR}/invoice-error.log
    CustomLog ${APACHE_LOG_DIR}/invoice-access.log combined
</VirtualHost>
Enable the site and restart Apache:
sudo a2ensite invoice.conf
sudo systemctl restart apache2

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Database Schema

The simple_invoice.sql file creates the following tables:

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Core Tables

CREATE TABLE IF NOT EXISTS `users` (
  `user_id` int(11) NOT NULL AUTO_INCREMENT,
  `firstname` varchar(20) COLLATE utf8_unicode_ci NOT NULL,
  `lastname` varchar(20) COLLATE utf8_unicode_ci NOT NULL,
  `user_name` varchar(64) COLLATE utf8_unicode_ci NOT NULL,
  `user_password_hash` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `user_email` varchar(64) COLLATE utf8_unicode_ci NOT NULL,
  `date_added` datetime NOT NULL,
  PRIMARY KEY (`user_id`),
  UNIQUE KEY `user_name` (`user_name`),
  UNIQUE KEY `user_email` (`user_email`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

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Default Data

The SQL import creates a default admin user: 
INSERT INTO `users` VALUES
(1, 'Obed', 'Alvarado', 'admin', 
 '$2y$10$MPVHzZ2ZPOWmtUUGCq3RXu31OTB.jo7M9LZ7PmPQYmgETSNn19ejO', 
'admin@admin.com', '2016-05-21 15:06:00');
Security Notice: The default admin password is admin. Change this immediately after first login.

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Post-Installation

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Verify Installation

After installation, verify everything is working:
  1. Navigate to your Simple Invoice URL
  2. You should see the login page
  3. Log in with default credentials (username: admin, password: admin)
  4. Check that all menu items are accessible:
    • Facturas (Invoices)
    • Clientes (Clients)
    • Productos (Products)
    • Usuarios (Users)

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File Permissions

Ensure proper file permissions (Linux/Unix): 
# Set ownership
sudo chown -R www-data:www-data /var/www/html/simple_invoice

# Set directory permissions
sudo find /var/www/html/simple_invoice -type d -exec chmod 755 {} \;

# Set file permissions
sudo find /var/www/html/simple_invoice -type f -exec chmod 644 {} \;

# Make upload directories writable
sudo chmod -R 775 /var/www/html/simple_invoice/img

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Configuration Options

Key configuration files:
  • config/db.php - Database connection settings
  • config/conexion.php - Database connection function
  • config/tcpdf_config.php - PDF generation settings

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Troubleshooting

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Common Issues

Error: mysqli_connect(): (HY000/1045): Access deniedSolution: Verify credentials in config/db.php match your MySQL user and password.
define('DB_USER', 'root');  // Check this
define('DB_PASS', '');      // And this
Error: Blank page or 500 errorSolution: Enable PHP error reporting to see the actual error:
error_reporting(E_ALL);
ini_set('display_errors', 1);
Add this to the top of index.php temporarily.
Error: Table doesn’t exist errorsSolution: Ensure you imported simple_invoice.sql correctly:
mysql -u root -p simple_invoice < simple_invoice.sql
Verify tables exist:
USE simple_invoice;
SHOW TABLES;
Error: Simple PHP Login does not run on a PHP version smaller than 5.3.7Solution: Upgrade PHP to at least version 5.3.7, preferably 7.x or 8.x for better performance.
# Check current version
php -v

# Ubuntu/Debian upgrade
sudo apt install php7.4

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Next Steps

Now that Simple Invoice is installed, proceed to the Quick Start guide to create your first invoice.

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