Here are a couple of handy Google Chrome extensions that I came across the other day.
PHP Console
PHP Console can display PHP errors and var dumps in the Google Chrome Developer Console and notification popups. It can also execute PHP code remotely, with the help of this server side library.
JavaScript Errors Notifier
JavaScript Errors Notifier lets you know of any JavaScript errors either with an icon highlight, or with a popup window. This makes things a lot easier to notice.
This extension is rebuilt and republished again here! https://chrome.google.com/webstore/detail/javascript-errors-notifie/lplhclpeegjedapdliokcacmphgcnlnd?hl=en&authuser=0 and you can read about the change here https://github.com/barbushin/javascript-errors-notifier/issues/101