Problem in saving attached image with task in ZOHO PROJECT API for PHP.

Problem in saving attached image with task in ZOHO PROJECT API for PHP.

Hello ,
I am using zoho project API i my PHP project .
I got full download path like 
"https://projects.zoho.com/portal/jigpatel/saveAttachment/New_Changes.png?file=ac27703bbe794cae5fe2adf332234549512ea65808268c0b363ac14d75338fa8"

but it can't download without login.
In my application i need to download all images first to my server.
so,can any one done this before in PHP ?
Please help me to solve out this.

Thanks !