demo.sh

#! /bin/bash

# recursively searching current directory for "foo" in PHP files and replace it with "bar"
for i in `find . -depth -name "*.php" -exec grep -Hni "foo" | awk -F: '{print $1}'`; do
    if [ -f "$i" ]; then
        sed -i ".old" -e "s/foo/bar/g' "$i"
    fi
done;