Will only work on Windows based servers, but how about:
<?php
// capture the screen
$img = imagegrabscreen();
imagepng($img, 'screenshot.png');
?>
Or:
<?php
// Capture the browser window
$Browser = new COM('InternetExplorer.Application');
$Browserhandle = $Browser->HWND;
$Browser->Visible = true;
$Browser->Fullscreen = true;
$Browser->Navigate('http://www.stackoverflow.com');
while($Browser->Busy){
com_message_pump(4000);
}
$img = imagegrabwindow($Browserhandle, 0);
$Browser->Quit();
imagepng($img, 'screenshot.png');
?>
Searching is useful for a fast answer ;)
Website screenshots using PHP