Easiest way to install the current version for PHP5 on Debian is as below. You may need additional packages if you don't have the basics like GCC installed. Also, start in a temporary directory since many junk files are created.
sudo apt-get install php5-dev dh-make-php fakeroot xsltproc
dh-make-pecl --only 5 rar
sudo dpkg -i ../php5-rar_3.0.0-1_amd64.deb