Set cron job for absolute path
wget --spider 'http://www.xyz.com/controllera/functiona'

/usr/bin/php /path/to/index.php controller/method

wget http://www.xyz.com/controllera/functiona

# run everyday at 3 pm a GET HTTP request
   0 15 * * *  /usr/bin/wget http://www.xyz.com/controllera/functiona