I dont know if this is even possible inside of gedit, i know there are third party editors that will do this but i like gedit and would like to know if anyone knows of such a plugin because i cant find one.
Yes, phplint . You can get it from :
Direct link https://github.com/janpecha/gedit-phplint
To install one of these plugins, you need to download the files and put them in your ~/.local/share/gedit/plugins/ directory (which may need to be created). They need to be in that exact directory; subdirectories are not scanned for plugins.
mkdir -p ~/.local/share/gedit/plugins/
Then on the second link I gave you, click the "Download Zip" button on the left , unzip the archive to