i have big problem in HTTP_REFERER - php

Question

now i make simple system in my site and this its code
if(stc($_SERVER['HTTP_REFERER'], $_SERVER['HTTP_HOST'])){
//download directly
}else{
//open page first
}
function stc($haystack, $needle, $offset=0) {
return strpos(strtoupper($haystack), strtoupper($needle), $offset);
}
if any one enterd the link from my site its download directly ok
and if from any other sites its open a page
now its working great
but if any one installed any downloader such as inernet download manager
its make the link directly not going to page first i think because its make HTTP_REFERER null
now how i can doing the system like rapidshare.com

Answer 1

strpos can return 0.... 0 as in the pos a needle can be (at the first postion in the haystack, first position in a string is 0).
strpos() return's false if the needle was not found.
0 & false are both the same in if statements...
$test = 0;
if (!$test) echo "0 is like false";
$test2 = false;
if (!$test2) echo "This one is also false..";
You have to make sure it's false or 0, this you can do with: ===
if (strpos() === false) echo "It's not found for sure!";
So your code becomes:
if(stc($_SERVER['HTTP_REFERER'], $_SERVER['HTTP_HOST']) !== false){
//download directly
}else{
//open page first
}