If I understand right, you need something like this:
$source = $_POST['source'];
if(preg_match('#http:\/\/(.*)#ui'))
echo htmlspecialchars(file_get_contents($source));
If I understand right, you need something like this:
$source = $_POST['source'];
if(preg_match('#http:\/\/(.*)#ui'))
echo htmlspecialchars(file_get_contents($source));