If you’ve used Eclipse PDT and you’ve tried launching Firefox as an external browser, you may find at times that Firefox rejects multiple instances of a browser session running by challenging you with a popup. The way around this is to
- launch the Eclipse Preferences, select General | Web Browser | Use external web browser.
- Make sure Firefox is checked
- Click on the Edit button
- For location, enter /usr/bin/open
- For Parameters, enter -a /Applications/Firefox.app %URL%
- Save and launch your Eclipse PHP debugger, and TADA!!