Question

After converting my canvas to a an image source using

 canvas.toDataURL("image/png");

and passing it to a php file, how do I save it as a .png image on the server?

Answer 1

It’s actually very simple, if you have allow-url-fopen enabled. PHP supports the data: URL scheme then, and automatically decodes base64 and urlencoding.

preg_match('#^data:[\w/]+(;[\w=]+)*,[\w+/=%]+$#', $data=$_POST["dataU"])
and
copy($data, "output.png");

But you could also just extract the part after the , and manually base64_decode() it.