Why did the king not want his daughter to be married with Aladdin?

It's not necessarily that the Sultan didn't want Princess Jasmine to marry Aladdin, the predicament they faced was that according to the Law, a Princess can only marry a Prince. That is why Aladdin wishes to become a Prince. However, by the end of the movie, it is agreed that despite of the Law Jasmine may choose whomever she wishes, regardless of their societal standing.