Emergence Documentation


Once a .php script within site-root begins handling a request, it can output whatever headers and content it wants.

Most responses will be rendered by the RequestHandler::respond method though. The static property RequestHandler::$responseMode determines what format a response will be rendered in, and defaults to 'html'. Scripts or extending classes may switch $responseMode to based on their own logic.

When RequestHandler::respond is invoked, it takes two parameters: $responseId and $responseData. Regardless of response mode, $responseId will always be provided to the client via the X-Response-ID response header.

Response Modes


This is the simplest response mode, $responseData is encoded to JSON and outputted with Content-Type: application/json


The default response mode, a dwoo template will be searched for in html-templates combining the $responseId with the request path from right-to-left. Output from the template will be returned to the client with Content-Type: text/html

To continue the example from the routing page, if the request handler at http://codeforphilly.org/projects/Code_for_Philadelphia/edit invoked RequestHandler::respond('projectEdit', ['success' => true, 'data' => $Project]), the site would search in this order to find the best template:

  1. html-templates/projects/Code_for_Philadelphia/edit/projectEdit.tpl
  2. html-templates/projects/Code_for_Philadelphia/projectEdit.tpl
  3. html-templates/projects/projectEdit.tpl
  4. html-templates/projectEdit.tpl

In the code for codeforphilly.org, #3 will match first and be used to render the responseData to HTML, with each key in the responseData array becoming a variable available from dwoo.


Handled the same way as html, but template output will be returned to the client with Content-Type: text/xml.


In 'return' mode, an array containing responseID and data will be returned from the respond() fuction to the caller.


A template is found following the same logic as for the 'html' response mode, but responseId is suffixed with .pdf first and the output from the template is written to /tmp and processed with wkhtmltopdf to be returned with Content-Type: application/pdf. For the example request described above, a template named projectEdit.pdf.tpl would need to be found.


The CSV::fromRecords method is used to attempt to render $responseData in CSV format with Content-Type: text/csv and Content-Disposition: attachment; filename=$responseId.csv

Emergence Development Roadmap

  • There should be a way for classes extending RequestHandler to declare a list of allowed response modes which will be automatically selected from based on the Accept requset header.