Ucwords() should have an optional parameter to set the minimum of characters a word must have to be capitalized. For example, sometimes I don't want to capitalize words with less than 3 characters. Examples:

New York Institute Of Photography
New York Institute of Photography (better)

My Web Site Is Cool With PHP
My Web Site is Cool With PHP (better)

Well, may the first word be capitalized by ucwords() even if its size is less than specified by the parameter? In any case we can capitalize it with ucfirst().  :-)

$str=ucfirst(ucwords(strtolower($str),3));