The issue has been discussed in the forum: https://forums.limesurvey.org/forum/can-i-do-this-with-limesurvey/142733-get-question-code-and-question-text-in-export-via-remote-control-api#251313

Using a PHP script to export responses via the API https://api.limesurvey.org/classes/remotecontrol_handle.html#method_export_responses , it is possible to get the question code AND question text in the column header by setting the $sHeadingType parameter to 'codetext', which is not documented in the API documentation.

[code] $response = $lsJSONRPCClient->export_responses($sessionKey, $surveyID, 'csv', 'en', 'complete', 'codetext', 'long'); [/code]

However, question code and question text get concatenated without a separator (unlike in the export via the web interface). This makes the heading difficult to read, for example "S1Q5What is your name?".

Specifying a codetextseparator in $aAdditionalOptions does not have any effect.
[code]('codetextseparator' => '. ')[/code]

Please allow users to define a custom codetextseparator in $aAdditionalOptions.