API php: "Hello World" test not working

tsp_dev — Wed, 27 Oct 2021 19:15:31 GMT

I'm trying to use the authorize.net API for the first time on my website. I've been trying to run the "hello world" test found here:

https://developer.authorize.net/hello_world.html

For some reason, the very first line breaks it. I've followed the instructions exactly, I updated and ran the composer file, and made the file called "charge-credit-card.php" and put in my ID and transaction key.

I am running php 5.6.40, which they say is high enough but I'm suspicous that could be an issue. When commenting out lines, I find that the very first line breaks the page, but some later ones are okay. the first line being " require 'vendor/autoload.php'; "

Can anyone think of reasons why this would not work? Or any other steps required to use the Authorize.net API?

topic API php: "Hello World" test not working in Integration and Testing

API php: "Hello World" test not working