"send images..."
I'm not sure what your intention is. You talk about about POSTs but sending and an API. And this topic is in PHP. So I assume it's a server-side solution. I'm not sure I understand why you'd not just let Apache deliver things upon request ... but clearly that's because I don't understand what you want

Hehe, sorry for not explaining myself clear enough, happens quite often :/
Anyway, the idea is simple: User has a script that sends image files from computer A to computer B.
So what I was thinking was that I could just do API that accepts POSTs. So you could do $post = array('user_id' => 'f00', 'api_key' => '0F0F', 'image' => base64_encode($imagefile)); and then just send it forward as POST with CURL. But I'm not sure if this is the best day to do it. Everybody seems to be saying that I should do RESTful API but I haven't ever done one and I'm not sure it's worth the hassle when I just need to get this done asap.