The phrase "has to dinner" can be easily replaced by numerous synonyms that can help diversify and enrich the vocabulary of your writing or speech. Some synonyms include "needs to dine," "must eat," "is required to have dinner," "ought to sup," and "is obligated to feast." Depending on the context and tone of your sentence, you may want to explore further variations such as "has a social engagement for dinner," "plans to dine with guests," or "has scheduled a dinner appointment." By using synonyms, you can avoid repetition and make your language more interesting and varied, adding more nuance to the meaning of your words.