This article describes basic, but still efficient ways of promoting your Classifieds Ads site, if you are local news portal, local magazine
First, quite obvious, use resources at your disposal. Advertise your Classified site on your news portal / magazine site. And link to it from every page. At launch you can add some advertisement banners and articles informing your user base about addition or upgrade of your PHP Classifieds Script.
If you utilize social media, inform your users on sites like: Facebook, Instagram, Twitter, YouTube and others.
Buy physical advertisement, in places like City Center, local marketplace, Fleamarket, Swimming Pool and other places that people visit in their leisure time.
Also make sure that your classified site is not empty. Try getting on board some local used car dealers, old items collector, add to your site some publicly displayed classified listings, that people didn’t put on the internet yet.