Missing API key for Google Cloud - php

Question

I'm attempting to use Google's Natural Language API for PHP, and having followed the instructions, I'm getting an error in the application I've written:
Fatal error: Uncaught Google\Cloud\Core\Exception\ServiceException: {
"error": { "code": 403, "message": "The request is missing a valid API
key.", "status": "PERMISSION_DENIED" } }
I've downloaded the account key file, run the export, but I get the 403 error.
I've created a symbolic link to the file in the project folder, run the export, but I get the 403 error.
I placed the export in the ".bash_profile" file, exited the terminal session, but I get the 403 error.
Provide authentication credentials to your application code by setting
the environment variable GOOGLE_APPLICATION_CREDENTIALS. Replace
[PATH] with the file path of the JSON file that contains your service
account key, and [FILE_NAME] with the filename. This variable only
applies to your current shell session, so if you open a new session,
set the variable again.
When I ran: echo $GOOGLE_APPLICATION_CREDENTIALS the export isn't there, so I ran it again, but I get the 403 error.
I followed the documentation to the letter, and I've gone through it three times, and each time I get the same 403 error.
I see no instructions asking me to store a string value for the API key in the application, but I've found a number of people recommending that, but not provide an example of how or where.
So, some advice would be welcome!

Answer 1

simply do not use an export; while your ~/.bashrc is not apache's .bashrc.
but add the path to the file directly into the PHP code; eg. into a config.php.
or use putenv('GOOGLE_APPLICATION_CREDENTIALS=/var/www/[FILE_NAME].json');
while preventing HTTP access to that file with .htaccess.
or one can even setup with .htaccess, alike
SetEnv GOOGLE_APPLICATION_CREDENTIALS "/var/www/[FILE_NAME].json"