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Project Overview

The inventory management system follows a simple, functional file structure organized by feature modules. Each directory contains related PHP files that handle specific aspects of the application.

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Directory Tree

source/
├── index.php                 # Main dashboard/home page
├── config/                   # Configuration files
│   └── conexion.php         # Database connection
├── auth/                     # Authentication module
│   ├── login.php            # User login
│   └── logout.php           # Session termination
├── productos/                # Product management module
│   ├── listar.php           # List all products
│   ├── crear.php            # Create new product
│   ├── editar.php           # Edit existing product
│   └── eliminar.php         # Delete product
└── movimientos/              # Inventory movement module
    ├── entrada.php          # Register product entry
    └── salida.php           # Register product exit

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File Descriptions

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Root Level

Purpose: Landing page after successful login, displays user information and session status.Location: /index.phpKey Features:
  • Session validation
  • Redirects to login if not authenticated
  • Displays username and role
  • Logout link
session_start();

if (!isset($_SESSION['usuario'])) {
    header("Location: auth/login.php");
    exit();
}

echo "Bienvenido, " . $_SESSION['usuario'];
echo "Rol: " . $_SESSION['rol'];
Session Requirements:
  • $_SESSION['usuario'] - User’s name
  • $_SESSION['rol'] - User’s role (admin/usuario)

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config/

Purpose: Establishes MySQL database connection using MySQLi.Location: /config/conexion.phpConfiguration:
$host = "localhost";      // Database host
$user = "root";           // Database username
$pass = "";               // Database password
$db   = "bd_inventario";  // Database name

$conn = new mysqli($host, $user, $pass, $db);
Usage Pattern: Included at the top of every file that needs database access:
include("../config/conexion.php");
// or
include("config/conexion.php");
Global Variable:
  • $conn - MySQLi connection object used throughout the application

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auth/

Authentication module handles user login and session management.
Purpose: Handles user login form and authentication logic.Location: /auth/login.phpFlow:
  1. Display login form (GET request)
  2. Process credentials (POST request)
  3. Query usuarios table by email
  4. Validate password (plain text comparison)
  5. Create session variables
  6. Redirect to main page
Form Fields:
  • correo (email) - User’s email address
  • password - User’s password
  • login (submit button)
Database Query:
$sql = "SELECT * FROM usuarios WHERE correo = '$correo'";
$resultado = $conn->query($sql);
$usuario = $resultado->fetch_assoc();
Session Creation:
$_SESSION['usuario'] = $usuario['nombre'];
$_SESSION['rol'] = $usuario['rol'];
header("Location: ../index.php");
Error Messages:
  • “Usuario no encontrado” - Email doesn’t exist
  • “Contraseña incorrecta” - Wrong password
Purpose: Destroys user session and redirects to login.Location: /auth/logout.phpImplementation:
session_start();
session_destroy();
header("Location: login.php");
exit();
Accessed From:
  • Main dashboard logout link
  • Manual navigation

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productos/

Product management module implements full CRUD operations.
Purpose: Displays all products in a table with action links.Location: /productos/listar.phpQuery:
$resultado = $conn->query("SELECT * FROM productos");
Display Columns:
  • ID
  • Nombre (name)
  • Código (product code)
  • Precio (price)
  • Stock (current quantity)
  • Acciones (edit/delete links)
Navigation Links:
  • crear.php - Add new product
  • editar.php?id={id} - Edit product
  • eliminar.php?id={id} - Delete product
  • ../movimientos/entrada.php - Register entry
  • ../movimientos/salida.php - Register exit
  • ../index.php - Back to home
Features:
  • Delete confirmation dialog
  • Direct links to movement registration
  • Real-time stock display
Purpose: Form and logic for creating new products.Location: /productos/crear.phpForm Fields:
  • nombre - Product name (text, required)
  • codigo - Product code/SKU (text, required)
  • precio - Price (number, decimal, required)
Insert Query:
$sql = "INSERT INTO productos (nombre, codigo, precio)
        VALUES ('$nombre', '$codigo', '$precio')";

if ($conn->query($sql)) {
    header("Location: listar.php");
}
Note: Initial stock is set to 0 by database default. Stock is managed through movimientos.
Purpose: Form and logic for updating product information.Location: /productos/editar.phpURL Parameter:
  • id - Product ID to edit (GET parameter)
Load Product:
$id = $_GET['id'];
$producto = $conn->query("SELECT * FROM productos WHERE id=$id")
            ->fetch_assoc();
Update Query:
$conn->query("UPDATE productos 
              SET nombre='$nombre', codigo='$codigo', precio='$precio'
              WHERE id=$id");
Editable Fields:
  • nombre
  • codigo
  • precio
Note: Stock is NOT editable here - it’s managed automatically through movimientos.
Purpose: Deletes a product from the database.Location: /productos/eliminar.phpURL Parameter:
  • id - Product ID to delete (GET parameter)
Implementation:
$id = $_GET['id'];
$conn->query("DELETE FROM productos WHERE id=$id");
header("Location: listar.php");
Cascade Effect: Due to foreign key constraint, all related movimientos records are automatically deleted (ON DELETE CASCADE).Confirmation: Handled by JavaScript confirm dialog in listar.php:
onclick="return confirm('¿Eliminar producto?')"

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movimientos/

Inventory movement module handles stock entries and exits.
Purpose: Register incoming inventory and increase stock.Location: /movimientos/entrada.phpForm Fields:
  • producto_id - Product selection dropdown (from productos table)
  • cantidad - Quantity to add (number, min=1)
Two-Step Process:Step 1: Record Movement
$conn->query("INSERT INTO movimientos (producto_id, tipo, cantidad)
              VALUES ($producto_id, 'entrada', $cantidad)");
Step 2: Update Stock
$conn->query("UPDATE productos 
              SET stock = stock + $cantidad 
              WHERE id = $producto_id");
Flow:
  1. Display form with product dropdown
  2. User selects product and enters quantity
  3. Insert movement record
  4. Increment product stock
  5. Redirect to product list
Purpose: Register outgoing inventory and decrease stock with validation.Location: /movimientos/salida.phpForm Fields:
  • producto_id - Product selection dropdown
  • cantidad - Quantity to remove (number, min=1)
Three-Step Process:Step 1: Validate Stock
$producto = $conn->query("SELECT stock FROM productos WHERE id=$producto_id")
            ->fetch_assoc();

if ($producto['stock'] >= $cantidad) {
    // Proceed with exit
} else {
    $error = "Stock insuficiente";
}
Step 2: Record Movement
$conn->query("INSERT INTO movimientos (producto_id, tipo, cantidad)
              VALUES ($producto_id, 'salida', $cantidad)");
Step 3: Update Stock
$conn->query("UPDATE productos 
              SET stock = stock - $cantidad 
              WHERE id = $producto_id");
Validation: Prevents negative stock by checking available quantity before processing.

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Common Patterns

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Session Management

Every protected page follows this pattern: 
session_start();
include("../config/conexion.php");

// Check authentication
if (!isset($_SESSION['usuario'])) {
    header("Location: ../auth/login.php");
    exit();
}

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Form Processing

All forms use POST method with named submit buttons: 
if (isset($_POST['button_name'])) {
    // Process form data
    $field = $_POST['field_name'];
    
    // Execute query
    $conn->query($sql);
    
    // Redirect on success
    header("Location: destination.php");
    exit();
}

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Database Operations

Query Execution: 
$resultado = $conn->query($sql);
Fetch Single Row: 
$row = $resultado->fetch_assoc();
Fetch Multiple Rows: 
while ($row = $resultado->fetch_assoc()) {
    // Process each row
}

index.php
  └─> productos/listar.php (main hub)
       ├─> crear.php
       ├─> editar.php?id=X
       ├─> eliminar.php?id=X
       ├─> movimientos/entrada.php
       └─> movimientos/salida.php

auth/
  ├─> login.php (entry point)
  └─> logout.php (exit point)

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Module Dependencies

config/conexion.php
  ├─ Required by: ALL modules
  └─ Provides: $conn (MySQLi object)

auth/login.php
  ├─ Creates: $_SESSION['usuario'], $_SESSION['rol']
  └─ Required by: ALL protected pages

productos/*
  ├─ Depends on: config/conexion.php, session
  └─ Used by: movimientos/*

movimientos/*
  ├─ Depends on: config/conexion.php, session, productos table
  └─ Modifies: productos.stock

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File Naming Conventions

  • Module directories: lowercase, plural (productos, movimientos)
  • PHP files: lowercase, descriptive verbs (crear, editar, eliminar, listar)
  • Action files: verb-based naming (entrada, salida, login, logout)
  • Config files: descriptive nouns (conexion)

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HTTP Methods

  • GET: Display forms, list data, navigation
  • POST: Submit forms, create/update/delete operations
  • URL Parameters: Pass entity IDs (e.g., ?id=5)

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Next Steps

Database Schema

Explore the complete database structure

Contributing

Learn how to contribute to the project

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