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You probably shouldn't be using a cookie for your purposes anyway - all people have to do is delete their temp. internet files and poof....no cookies. If a user deletes the cookie before they download your file, then they won't get access to it. The best solution is as follows: Every time a user requests a file, then create a key and add it to a database (MySQL, .txt file, etc). E-mail the user they key and ask them for it when they try to download the file. Once they enter the key and download the file, then remove that key from your database and there you are, a one time download.

I have some experience with cookies. I would like to help you out on this project. I'll give you the cookie101 class. First, I will show you how to set the date of expiry in a cookie. Next, cookie retrieval is pretty basic. For this simple cookie we want it to expire in 7 days. You decide if it's 7 days or 10 days. Within this time before the cookie expires users can download a file only once. Check the count of downloads against the cookie in a database. You need some way of collecting email addresses with a database. We need to keep email addresses out of the cookies and any sensitive information. Do you know SQL? Keep it simple.


PHP Sessions are POST values for passing into other pages. I do this for most of my time in my web applications. It makes it very accessible for the quick form widget to submit values to a larger form. These sessions will hold a count value on visited pages. The first project with cookies we have to store the visitors email addresses. As with  getting to know MySQL. MySQL is the most used database with PHP and can be used with any other server-side scripting language. Here is the acronym for LAMP or WAMP which is Linux, Apache, MySQL and PHP or Windows, Apache, MySQL and PHP respectively.

Already i  have implemented same in my project, can be deliver as per your requirment