PHP: create image with ImagePng and convert with base64_encode in a single file?

I have created an image with ImagePng(). I dont want it to save the image to the file system but want to output it on the same page as base64 encode inline Image, like

print '<p><img src="data:image/png;base64,'.base64_encode(ImagePng($png)).'" alt="image 1" width="96" height="48"/></p>';

which does not work.

Is this possible in a single PHP file at all?

Thanks in advance!