If a WordPress installation is protected via
.htaccess basic auth, the requests against the WooCommerce REST API with the PHP library do not work. I did not find the GitHub issue where someone said that CURL could be used to set the login credentials, but with that information, I found a question and the answers on Stack Overflow, that helped me:
$ch = curl_init(); curl_setopt( $ch, CURLOPT_USERPWD, 'user:password' );
I inserted these two lines at the beginning of my script and replaced
password with the actual login data. With that, the requests against the protected installation worked.