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).
注意: 本函数可安全用于二进制对象。
See also strtoupper(), strtolower() and ucfirst().