Returns a string with the first character of each word in str capitalized, if that character is alphabetic.
The definition of a word is any string of characters that is immediately after a whitespace (These are: space, form-feed, newline, carriage return, horizontal tab, and vertical tab).
Megjegyzés: Ez a függvény "binary-safe", azaz helyesen kezeli a 127-es ASCII kód feletti karaktereket is.
See also strtoupper(), strtolower() and ucfirst().