http://cubicspot.blogspot.ca/2013/03/just-use-grep-dont-use-find-grep-xargs.html

Previously, I used to use:

 
find . | grep css| xargs grep "sidebar" -sl

This command works much better, faster and allows for the use of special characters in the search string.

 
grep -nir --include="*.php" "my_function" .

Here is sample output when running the following command:

 
root@t605:/etc# grep -nir --include="*" "10.10.0" .