Rob Allen has a new post to his site showing how you can customize the Whoops output in a Zend Expressive application. Whoops is a package that provides more well-structured and more attractive error output when an issue comes up.

I find the Whoops error handler page in Expressive quite hard to read and particularly dislike that the error message displayed in the top left is hidden if it's more than a few words long.

To fix this, I discovered that you can provide a custom CSS file to the PrettyPrintHandler and then override to your heart's content! One way to do this is to add a delegator factory to add the additional functionality, so let's do that.

He then includes the configuration changes you'll need to make in the Expressive setup to have it recognize the factory and be able to use it as a dependency. He then includes the code to create the factory itself, adding a path to the local CSS files and pushing the custom whoops.css file into the page handler. Example CSS is included showing an update to the display of the main message, removing the need for a mouseover to view it.