PHP Download File

Summary: in this tutorial, you will learn how to download a file in PHP using the readfile() function.

Introduction to the PHP readfile() function

The readfile() function reads data from a file and writes it to the output buffer.

Here’s the syntax of the readfile() function:

readfile ( 
    string $filename , 
    bool $use_include_path = false , 
    resource $context = ? 
) : int|falseCode language: PHP (php)

The readfile() function has the following parameters:

• $filename is the path to the file.
• $use_include_path if set to true, the function will search for the file in the include path.
• $context specifies the stream context.

The readfile() function returns the number of bytes if it successfully reads data from the file, or false if it fails to read.

PHP download file example

The following example shows how to download the readme.pdf file using the readfile() function example.

<?php

$filename = 'readme.pdf';

if (file_exists($filename)) {
	header('Content-Description: File Transfer');
	header('Content-Type: application/octet-stream');
	header('Content-Disposition: attachment; filename="' . basename($filename) . '"');
	header('Expires: 0');
	header('Cache-Control: must-revalidate');
	header('Pragma: public');
	header('Content-Length: ' . filesize($filename));
	readfile($filename);
	exit;
}Code language: HTML, XML (xml)

PHP download file with a download rate limit

To set a download rate limit, you use the following script:

<?php

$file_to_download = 'book.pdf';
$client_file = 'mybook.pdf';

$download_rate = 200; // 200Kb/s

$f = null;

try {
	if (!file_exists($file_to_download)) {
		throw new Exception('File ' . $file_to_download . ' does not exist');
	}

	if (!is_file($file_to_download)) {
		throw new Exception('File ' . $file_to_download . ' is not valid');
	}

	header('Cache-control: private');
	header('Content-Type: application/octet-stream');
	header('Content-Length: ' . filesize($file_to_download));
	header('Content-Disposition: filename=' . $client_file);

	// flush the content to the web browser
	flush();

	$f = fopen($file_to_download, 'r');

	while (!feof($f)) {
		// send the file part to the web browser
		print fread($f, round($download_rate * 1024));

		// flush the content to the web browser
		flush();

		// sleep one second
		sleep(1);
	}
} catch (\Throwable $e) {
	echo $e->getMessage();
} finally {
	if ($f) {
		fclose($f);
	}
}
Code language: HTML, XML (xml)

How it works.

• First, define the path to the file ($file_to_download) to download and the name of the downloaded file ($client_file).
• Next, define the download rate ($download_rate) and set it to 200 Kb/s
• Then, throw an exception if the file doesn’t exist or is not a regular file.
• After that, read the part of the file and sleep for 1 second until the no more file data to read.
• Finally, close the file using the fclose() function.

Summary

• Use the readfile() function to force a file download in PHP.