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Force Download Dialog Boxes
By Patrick Lin
When we browse the web, we click on links. That’s what makes the web a web – the links between pages. Sometimes, those links lead us not to pages, but to files. Many types of files pop up dialog boxes prompting downloads – executables, videos, etc.
However, certain filetypes, thanks to modern web browsers, are rendered as an in-browser page, such as images, PDFs, and MP3s. While this may be a convenience, at times we may wish to force the user to download the files, not just view them in their browser.
In this article I will show two easy ways to do this. The first is using .htaccess, and the second is using PHP.
In your .htaccess file, add the following line for each extension you wish to force download:
AddType application/octet-stream extension
For example, if I wanted to force PDFs and MP3s to download, I would do this:
AddType application/octet-stream .pdf AddType application/octet-stream .mp3
It’s really quite simple, and can be done quickly.
The PHP version is a bit more complicated, but can be useful if you want to have a bit more control. For example, you can use download IDs instead of the filename to prevent direct hotlinking. For example, you can assign the ID “3148″ to “BusinessPlan.pdf” and do a forced download.
The basic code looks like this:
<?php header('Content-Disposition:inline;filename="'.$file.'"'); header('Content-Transfer-Encoding:Binary'); header('Content-length:'.filesize($file)); header('Content-Type:application/octet-stream'); header('Content-Disposition: attachment; filename="'.$file.'"'); readfile("$file"); ?>
Of course, this is a huge security hole if you use the structure
download.php?file=BusinessPlan.pdf, as anyone can access any file on your webserver. Thus, steps should be taken to secure the user input, or use a database of IDs.
Of course, if you’re just forcing download and don’t need extra control over the download process, you should use the .htaccess version, as it is much simpler and easier to use.
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