To customize the "X-Powered-By" header returned to the client browser:

Use the [web_response->replaceHeader] method.

Code

web_response->replaceHeader('X-Powered-By' = 'Lasso 9 + LEAP 5')
// return the web_response->headers for demonstration purposes
web_response->headers

Result

array((Content-Type = text/html; charset="UTF-8"), (X-Powered-By = Lasso 9 + LEAP 5))

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To force a file to be downloaded and set as an MS Excel file type:

Use the [web_response->replaceHeader] method.

Code

web_response->replaceHeader('Content-type' = 'application/vnd.ms-excel')
web_response->replaceHeader('Content-Disposition' = 'attachment;filename=your_file_name.xls')