In the book of Ecclesiastes (Kohelet) there are used two very interesting words. "Pardes" in 2:5 and "Pitgam" in 8:11. "Pardes" is also seen in the book of Song Of Songs (Shir HaShirim) 4:13. Why are these words interesting? Because they are words borrowed from the Persian language.
Here is the etymology of the word "pardes": it is derived from the Old Persian "pairidaeza" which can be broken down in Farsi into pairi (around) and daeza (wall). It describes an enclosed garden. The word has even been found in the ancient scripture Avesta of the Zoroastrian faith. It is the source of the English word "paradise."
How could Solomon have known of and used Persian words if Persia had never come in contact with Israel during the proposed time of Solomon's lifetime? The use of these foreign words in these books necessarily pushes the writing of the texts several centuries after Solomon's death until at least when Israel comes under Persian rule.
So did Solomon write these books? It seems doubtful.