This article has been written before more than 24months, information might old.
As you probably know running PHP on Windows is a bad idea as you can get in a plethora of problems even for a simple development setup but, when you want to test a quick script or you just want to write maybe a solution to an algorithmic problem found on some type of programmer improvement site that accepts solutions in PHP you can use of course some prebuild windows binaries from windows.php.net.
Anyway, the main gist of this mini-post is that, I found a recurring bug with CURL library, the bug has been reported before and it consists in the fact that the library will not load(even if you set up correctly php.ini) you and no starting error will be generated so you will inside a PHP script that uses CURLthe following error:
Call to undefined function curl_init()
In my case, I was updating from version 7.0.9 to 7.0.24, so the quick and dirty solution is just to replace the php_curl.dll from your extension folder with one from a previous version of PHP that loaded( perhaps is best that versions should not be very distant). So obvious I didn’t try to get a more recent version of php_curl I just used the one from 7.0.9 and after that, I didn’t have any problem.
I have seen on the bug reporting pages of PHP that this problem was also sometimes present in the previous major version of PHP 5.6.