How to get file download url using api in php

The standard way to download a file via the Dropbox API is the /2/files/download endpoint. That returns the file data directly in the response body.

If you do need a URL that you can use to download the file, you can call /2/files/get_temporary_link. That will return a link that you can use to access the file data later via a GET request. Note that these links are only valid for four hours though.

Thanks for your reply

but I want file download link which any time any one can download file directly from my dropbox storage from my site using this URL.

How to get that link using API or PHP 

If you need a non-temporary link, you can instead use /2/sharing/create_shared_link_with_settings to get a shared link.

You can also modify those shared links for different behaviors as documented here.