I have a PHP script that connects to an api and posts information to their systems, but when its trying to connect it throws a fatal error:
Fatal error: Unca
First error message suggests problems with apitestserver - it returns error code 500, which states for "Internal server error".
Second one informs that PHP can't resolve host name into IP address - I'd look into DNS configuration and/or hosts file.
Apparently 'fopen' function does not return proper stream. There can be many possibilities when that happens, but according to PHP manual, fopen function on fail should present E_WARNING message with proper commentary. It is possible that you have errors of that class silenced - call error_reporting(E_ALL) at the beginning of your script and look for some relevant error messages.