Split string on non-alphanumerics in PHP? Is it possible with php's native function?

I was trying to split a string on non-alphanumeric characters or simple put I want to split words. The approach that immediately came to my mind is to use regular expressions.

Example:
$string = 'php_php-php php';
$splitArr = preg_split('/[^a-z0-9]/i', $string);

But there are two problems that I see with this approach.

1. It is not a native php function, and is totally dependent on the PCRE Library running on server.
2. An equally important problem is that what if I have punctuation in a word
   Example:
   $string = 'U.S.A-men's-vote';
$splitArr = preg_split('/[^a-z0-9]/i', $string);
   Now this will spilt the string as [{U}{S}{A}{men}{s}{vote}]
   But I want it as [{U.S.A}{men's}{vote}]

So my question is that:

• How can we split them according to words?
• Is there a possibility to do it with php native function or in some other way where we are not dependent?

Regards

Sounds like a case for str_word_count() using the oft forgotten 1 or 2 value for the second argument, and with a 3rd argument to include hyphens, full stops and apostrophes (or whatever other characters you wish to treat as word-parts) as part of a word; followed by an array_walk() to trim those characters from the beginning or end of the resultant array values, so you only include them when they're actually embedded in the "word"