How to create own config for uhttpd?

I include a php in the my custom firmware, so I need to include a some string into default uhttpd config.

In your buildroot:

$ mkdir -p files/etc/uci-defaults/
$ cat <<EOT > files/etc/uci-defaults/99-uhttpd-set-interpreter

uci add_list uhttpd.main.interpreter='.php=/usr/bin/php-cgi'
uci commit uhttpd

exit 0

Then rebuild the image with make. The command above creates a firstboot script that modifies /etc/config/uhttpd before the services are started.

Heh. After some years I'll forget what my actual config is modified in some place.

Alternatively you can simply ship a complete uhttpd config by providing a files/etc/config/uhttpd in your buildroot.