I. Database Setup (MySQL)
The first step is setting up a database to store file metadata (filename, upload date, file path, etc.).
file_management
.files
with the following structure:CREATE TABLE files ( id INT AUTO_INCREMENT PRIMARY KEY, filename VARCHAR(255) NOT NULL, filepath VARCHAR(255) NOT NULL, upload_date DATETIME DEFAULT CURRENT_TIMESTAMP );
id
: Unique identifier for each file.filename
: Original name of the uploaded file.filepath
: Path to the file on the server. Ideally, store files outside the web root.upload_date
: Timestamp indicating when the file was uploaded.II. HTML Form (upload.html)
This form provides the interface for users to select and upload files.
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>File Upload</title> <link rel="stylesheet" href="style.css"> </head> <body> <div class="container"> <h1>Upload a File</h1> <form action="upload.php" method="post" enctype="multipart/form-data"> <input type="file" name="fileToUpload" id="fileToUpload"> <button type="submit" name="submit">Upload</button> </form> <div id="uploadStatus"></div> </div> <script src="script.js"></script> </body> </html>
enctype="multipart/form-data"
: Crucial for handling file uploads. It specifies how the form data should be encoded.input type="file"
: The file selection input. name="fileToUpload"
is the name used to access the file data in PHP.button type="submit"
: Submits the form to the upload.php
script.div id="uploadStatus"
: A container to display upload progress or messages via JavaScript.III. PHP Upload Script (upload.php)
This script handles the file upload logic, including validation, storage, and database insertion.
<?php // Database Configuration $servername = "localhost"; $username = "your_username"; $password = "your_password"; $dbname = "file_management"; // Create connection $conn = new mysqli($servername, $username, $password, $dbname); // Check connection if ($conn->connect_error) { die("Connection failed: " . $conn->connect_error); } if (isset($_POST["submit"])) { $target_dir = "uploads/"; // Directory to store uploaded files (outside web root recommended) $target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]); $uploadOk = 1; $imageFileType = strtolower(pathinfo($target_file, PATHINFO_EXTENSION)); // Basic Validation // Check if file already exists if (file_exists($target_file)) { echo "Sorry, file already exists."; $uploadOk = 0; } // Check file size (example: limit to 5MB) if ($_FILES["fileToUpload"]["size"] > 5000000) { echo "Sorry, your file is too large."; $uploadOk = 0; } // Allow certain file formats (example: images) if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg" && $imageFileType != "gif" ) { echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed."; $uploadOk = 0; } // Perform the upload if ($uploadOk == 0) { echo "Sorry, your file was not uploaded."; } else { if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) { // Insert file information into the database $filename = basename($_FILES["fileToUpload"]["name"]); $filepath = $target_file; // Store the full path $sql = "INSERT INTO files (filename, filepath) VALUES ('$filename', '$filepath')"; if ($conn->query($sql) === TRUE) { echo "The file ". htmlspecialchars( basename( $_FILES["fileToUpload"]["name"])) . " has been uploaded."; } else { echo "Error: " . $sql . "<br>" . $conn->error; } } else { echo "Sorry, there was an error uploading your file."; } } } $conn->close(); ?>
"your_username"
, "your_password"
, and "file_management"
with your actual database credentials.$_FILES
Superglobal: Contains information about the uploaded file. $_FILES["fileToUpload"]
provides an array of details, including name, temporary location, size, etc.$target_dir
: Specifies the directory where uploaded files will be stored. It’s critically important to store this directory outside of your web server’s document root for security reasons. Create the uploads
directory if it does not exist and ensure the web server process has write permissions to it.move_uploaded_file()
: Moves the uploaded file from its temporary location to the specified $target_file
. This is the core file upload function.files
table. Storing the filepath allows you to later retrieve and serve the file for download.IV. Download Script (download.php)
This script handles the file download process, retrieving the path from the database and setting the appropriate headers.
<?php // Database Configuration (same as upload.php) $servername = "localhost"; $username = "your_username"; $password = "your_password"; $dbname = "file_management"; // Create connection $conn = new mysqli($servername, $username, $password, $dbname); // Check connection if ($conn->connect_error) { die("Connection failed: " . $conn->connect_error); } if (isset($_GET['id'])) { $id = $_GET['id']; // Fetch file information from the database $sql = "SELECT filename, filepath FROM files WHERE id = '$id'"; $result = $conn->query($sql); if ($result->num_rows > 0) { $row = $result->fetch_assoc(); $filepath = $row['filepath']; $filename = $row['filename']; // Verify file exists on the server: if (file_exists($filepath)) { header('Content-Description: File Transfer'); header('Content-Type: application/octet-stream'); header('Content-Disposition: attachment; filename="' . $filename . '"'); header('Expires: 0'); header('Cache-Control: must-revalidate'); header('Pragma: public'); header('Content-Length: ' . filesize($filepath)); readfile($filepath); exit; } else { echo "File not found."; } } else { echo "File not found in database."; } } else { echo "Invalid request."; } $conn->close(); ?>
$_GET['id']
: Retrieves the file ID from the query string (e.g., download.php?id=1
). This ID uniquely identifies the file to be downloaded.files
table to retrieve the filepath
associated with the given ID.header()
Functions: Set HTTP headers that instruct the browser how to handle the download. Content-Description: File Transfer
: Indicates that the response is a file to be downloaded.Content-Type: application/octet-stream
: Specifies the MIME type of the file (generic binary data).Content-Disposition: attachment; filename="..."
: Forces the browser to download the file with the specified filename.Content-Length
: Specifies the size of the file.readfile()
: Reads the file from the filesystem and outputs it to the browser. This is the core function that delivers the file content.V. File Listing and Download Links (index.php or similar)
A page to display the uploaded files and provide download links.
<?php // Database Configuration (same as upload.php) $servername = "localhost"; $username = "your_username"; $password = "your_password"; $dbname = "file_management"; // Create connection $conn = new mysqli($servername, $username, $password, $dbname); // Check connection if ($conn->connect_error) { die("Connection failed: " . $conn->connect_error); } $sql = "SELECT id, filename, upload_date FROM files"; $result = $conn->query($sql); echo "<h1>Uploaded Files</h1>"; echo "<ul>"; if ($result->num_rows > 0) { while($row = $result->fetch_assoc()) { echo "<li>"; echo $row["filename"] . " - Uploaded on: " . $row["upload_date"] . " - "; echo "<a href='download.php?id=" . $row["id"] . "'>Download</a>"; echo "</li>"; } } else { echo "No files uploaded yet."; } echo "</ul>"; $conn->close(); ?>
download.php
, passing the file’s ID as a query parameter (?id=...
).VI. JavaScript (script.js – for enhancements, e.g., progress display)
document.getElementById('fileToUpload').addEventListener('change', function (e) { const file = e.target.files[0]; if (file) { const fileSizeInMB = file.size / (1024 * 1024); const fileName = file.name; } });
This Javascript file provides interactive functionality to your uploader.
VII. CSS (style.css – for styling)
body { font-family: sans-serif; margin: 0; padding: 0; background-color: #f4f4f4; } .container { width: 80%; margin: 20px auto; background-color: #fff; padding: 20px; border-radius: 8px; box-shadow: 0 0 10px rgba(0, 0, 0, 0.1); } h1 { text-align: center; color: #333; } form { display: flex; flex-direction: column; align-items: center; } input[type="file"] { margin-bottom: 20px; padding: 10px; border: 1px solid #ddd; border-radius: 4px; } button[type="submit"] { padding: 10px 20px; background-color: #4CAF50; color: white; border: none; border-radius: 4px; cursor: pointer; font-size: 16px; } button[type="submit"]:hover { background-color: #3e8e41; } ul { list-style-type: none; padding: 0; } li { margin-bottom: 10px; } a { color: #007bff; text-decoration: none; } a:hover { text-decoration: underline; } #uploadStatus { margin-top: 20px; padding: 10px; border-radius: 4px; background-color: #f9f9f9; border: 1px solid #ddd; }
This CSS file provides aesthetic enhancement to your uploader.
Important Considerations and Security:
uploads
directory is outside of your web server’s document root. This prevents direct access to uploaded files via the browser, mitigating the risk of executing malicious code. Set appropriate file permissions on the uploads
directory to restrict access to the web server process.basename()
to extract the filename and remove or replace potentially dangerous characters.htmlspecialchars()
to escape HTML entities.upload_max_filesize
and post_max_size
directives in your php.ini
file accordingly.This comprehensive explanation covers the fundamental aspects of creating a file upload and download system. Applying strict validation, security measures and regularly maintaining the code remains crucial for a safe and trustworthy system.
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