How to Force File Download With PHP

As a software developer, you may come across a situation where you need to provide the functionality of downloading files on your website.

Whether it’s a PDF, an image, or any other type of file, you may want to ensure that the file is downloaded rather than displayed in the browser.

In this tutorial, we will look at how to force file downloads with PHP.

Forcing a file to download, instead of displaying it in the browser, is a common requirement for many websites.

For instance, you may have a PDF or an image file that you want to allow users to download.

By default, the browser may try to display the file in the browser, but with PHP, we can force the browser to download the file instead.

Understanding HTTP Headers

HTTP headers are key-value pairs that are sent between the client (browser) and the server.

These headers provide information about the request and response, including the type of content being sent, the encoding used, and more.

When it comes to forcing file downloads, HTTP headers play a crucial role.

Using the header() Function

The header() function in PHP is used to send HTTP headers to the client.

This function can be used to set the content type and encoding for the response, as well as other headers like the content-disposition header, which is what we will be using to force file downloads.

The syntax for the header() function is as follows:

header(string $header, [bool $replace = true], [int $http_response_code])

The first argument is the header string that we want to send, while the second argument is used to specify whether we want to replace any existing headers with the same name.

The third argument is optional and is used to set the HTTP response code.

Code Example

Here is a simple example of how to use the header() function to force a file download in PHP:

<?php

$file = 'sample.pdf';

header('Content-Type: application/pdf');
header('Content-Disposition: attachment; filename="'.basename($file).'"');
header('Content-Length: ' . filesize($file));

readfile($file);

In the above code, we first specify the path to the file that we want to download.

We then use the header() function to set the content type to application/pdf, which is the MIME type for PDF files.

Next, we set the content-disposition header to attachment, which tells the browser that we want to download the file, rather than display it in the browser.

We also set the filename to the name of the file that we want to download.

Finally, we use the filesize() function to get the size of the file and set the content-length header to this value.

This header is used to specify the size of the content being sent, and helps the browser to know when it has received the entire file.