How to force file download with PHP

Question

I want to require a file to be downloaded upon the user visiting a web page with PHP. I think it has something to do with file_get_contents, but am not sure how

Answer 1

In case you have to download a file with a size larger than the allowed memory limit (memory_limit ini setting), which would cause the PHP Fatal error: Allowed memory size of 5242880 bytes exhausted error, you can do this:

// File to download.
$file = '/path/to/file';

// Maximum size of chunks (in bytes).
$maxRead = 1 * 1024 * 1024; // 1MB

// Give a nice name to your download.
$fileName = 'download_file.txt';

// Open a file in read mode.
$fh = fopen($file, 'r');

// These headers will force download on browser,
// and set the custom file name for the download, respectively.
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="' . $fileName . '"');

// Run this until we have read the whole file.
// feof (eof means "end of file") returns `true` when the handler
// has reached the end of file.
while (!feof($fh)) {
    // Read and output the next chunk.
    echo fread($fh, $maxRead);

    // Flush the output buffer to free memory.
    ob_flush();
}

// Exit to make sure not to output anything else.
exit;