Currently I am working on a large php project and using xampp server and brackets IDE. Can anyone please tell me how to find the specific line or file where the variable is first defined.
you can use 3rd party applications like Actual Search and Replace
You can find the variable definition across files in brackets..
Shift+ctrl+F on windows.
You can also manually navigate to the option via the menu bar
Find > Find in Files
It will give you instances of the search string across all files in the project.