xxxxxxxxxx
curl -F "FIELDNAME=@FILE" http://URL
# FIELDNAME can be whatever you want, it is the key value of the form field
# the @ is important to point to a local file
xxxxxxxxxx
<?php
// You can not use any http url for the file path at curl. You have to use local file. So first download the file into a temporary directory.
file_put_contents("/var/tmp/xyz/output.jpg", file_get_contents("https://www.google.com/images/srpr/logo11w.png"));
//Then use this temporary file into your curl:
'image' => '@/var/tmp/xyz/output.jpg'
??