how to upload and retrieve image from php server on WP 8.1

Question

I am developing an app on windows phone 8.1. The problem is that how to upload an image and retrieve an image from php server on windows phone 8.1. I tried many times. i converted the image byte array into base64string and then send it to the php server but base64string cann't upload to the php server showing the base64string is too large. Then what is the solution of this?