Grep Search all files in directory for string1 AND string2

How can I make use of grep in cygwin to find all files that contain BOTH words.

This is what I use to search all files in a directory recursively for one word:

grep -r "db-connect.php" .

How can I extend the above to look for files that contain both "db-connect.php" AND "version".

I tried this: grep -r "db-connect.php\|version" . but this is an OR i.e. it gets file that contain one or the other.

Thanks all for any help