change filenames from .html to .php in current directory

file_renamer.py

import os


def rename_html_to_php():
    for filename in os.listdir("."):
        if os.path.isdir(filename):
            os.chdir("./"+filename)
            rename_html_to_php()
            os.chdir("..")
        if filename.endswith(".html"):
            print(filename, "changed !")
            os.rename(filename, filename.replace(".html", ".php"))


if __name__ == "__main__":
    rename_html_to_php()