Trigger action when file download actually completes
<p>Nowdays there are a lot of websites for files hosting (<code>uploading websites</code>) and it count for example point per complete download of certain file.</p>

<p><strong>My question</strong>
I want to understand what is the idea they are using !</p>

<p><em><strong>How</em></strong> does it only count on <strong><em>complete</em></strong> downloading of the file ?!
i mean if i <strong><em>canceled downloading</em></strong> of the file after it started , it won't count point!
how does it knew ! is there any php function that able to know if i canceled downloading certain exact file or not !</p>

<p>that question was all time in my mind and thinking about it but i can't understand how does it works or what is the idea behind it. ~ thanks</p>
