Issues with whois API request

[UmbHost Limtied]

When I try to make an API request (/includes/api.php?action=DomainWhois&responsetype=json) for the whois search I receieve a 500 error.

From the error in the log, it looks to be an issue with a vendor library:

{main} {"exception
[error] [WHMCS Application] ERROR: Laminas\HttpHandlerRunner\Exception\EmitterException: Unable to emit response; headers already sent in /home/wwwroot/vendor/laminas/laminas-httphandlerrunner/src/Exception/EmitterException.php:19 Stack trace: #0 /home/sites/25a/2/27a7ef7eec/my/wwwroot/vendor/laminas/laminas-httphandlerrunner/src/Emitter/SapiEmitterTrait.php(36): Laminas\HttpHandlerRunner\Exception\EmitterException::forHeadersSent() #1 /home/wwwroot/vendor/laminas/laminas-httphandlerrunner/src/Emitter/SapiEmitter.php(27): Laminas\HttpHandlerRunner\Emitter\SapiEmitter->assertNoPreviousOutput() #2 /home/wwwroot/includes/api.php(0): Laminas\HttpHandlerRunner\Emitter\SapiEmitter->emit(Object(WHMCS\Http\Message\JsonResponse)) #3

Interestingly the error only occurs with the external api, if I make an internal api request it works.

[andrezzz]

Hello,
How are you?

Just for the avoidance of doubt, can you show me the output of this request?

https://example.com/admin/whois.php?domain=REPLACE_WITH_DOMAIN

[UmbHost Limtied]

Sure it's below, as I say the internal API's all work great, it only breaks if I try to access it via the external api

[UmbHost Limtied]

This has been solved.

There was a stray space at the beginning of the configuration.php file