I need to do the following: The sense if I have a class dportfolio – show
a category dportfolio. Otherwise show usual category.

I use:

if ( class_exists( 'DPortfolio' ) ) {
      echo DPortfolio::instance()->dportfolio_get_category();
}; ?>

and when I try to add a second part of a code:

the_category(', ')

with if/else statement, I receive a php error.

Any suggestions to write this function in a correct way?