Is there any way of taking a screenshot of a website in PHP, then saving it to a file?
You can use https://grabz.it solution.
It's got a PHP API which is very flexible and can be called in different ways such as from a cronjob or a PHP web page.
In order to implement it you will need to first get an app key and secret and download the (free) SDK.
And an example for implementation. First of all initialization:
include("GrabzItClient.class.php");
// Create the GrabzItClient class
// Replace "APPLICATION KEY", "APPLICATION SECRET" with the values from your account!
$grabzIt = new GrabzItClient("Sign in to view your Application Key", "Sign in to view your Application Secret");
And screenshoting example:
// To take a image screenshot
$grabzIt->URLToImage("http://www.google.com");
// Or to take a PDF screenshot
$grabzIt->URLToPDF("http://www.google.com");
// Or to convert online videos into animated GIF's
$grabzIt->URLToAnimation("http://www.example.com/video.avi");
// Or to capture table(s)
$grabzIt->URLToTable("http://www.google.com");
Next is the saving.You can use one of the two save methods, Save
if publicly accessible callback handle available and SaveTo
if not. Check the documentation for details.