Prince Philip and Queen Elizabeth were married in 1947, and she took the throne and became queen in 1952. It was actually only in 1957 that Philip’s title was adjusted from Duke of Edinburgh to Prince. This was a decision made by the Queen herself and was in keeping with regular traditions around titles the monarchy observe.
The statement released by the palace at the time read: “The Queen has been pleased by Letters Patent under the Great Seal of the Realm bearing date 22nd February, 1957, to give and grant unto His Royal Highness the Duke of Edinburgh, K.G., K.T., G.B.E., the style and titular dignity of a Prince of the United Kingdom of Great Britain and Northern Ireland, Whitehall.”
Per monarchic traditions, a woman who marries a king may be called a queen, but the same does not apply to men who marry women. Per BBC News, “men who marry the monarch can't use the title king, which can only be used by male sovereigns.”
The next person who will be a British king is Prince Philip and Queen Elizabeth II’s son, Charles, Prince of Wales. Following Charles is his and Diana’s son, Prince William, whose eldest son with Kate Middleton, Prince George, is next in line for the title of king.