How to tar certain file types in all subdirectories?

Question

I want to tar and all .php and .html files in a directory and its subdirectories. If I use

tar -cf my_archive *

it tars all the files, which I

Answer 1

find ./ -type f -name "*.php" -o -name "*.html" -printf '%P\n' |xargs tar -I 'pigz -9' -cf target.tgz

for multicore or just for one core:

find ./ -type f -name "*.php" -o -name "*.html" -printf '%P\n' |xargs tar -czf target.tgz