在PNG中运行PHP

Question

I just wondered..
I've seen that some pictures can have "arguments" in an url like this:

http://example.com/images/picture.png?width=120

But when I google it, I get instructions where the result would be like this:

http://example.com/images/picture.php?width=120
(with header("Content-type: image/png") and so on)

(How) can i make a piece of php-code run in a "picture"?

Answer 1

In fact nobody cares about the file extension, it's just a hint usually for desktop applications only on how to handle the file, when you just double click it. However, behind the URL is a normal script of whatever language, that returns the header Content-Type: image/png alongside with an image as binary.

For example in PHP

// do something
header('Content-Type: image/png');
readfile('/local/path/to/a/prepared/image.png');