Capitalize first word of every sentence

<?
	function uc_sentences($sString)
	{
		$sString = strtolower($sString);
		$words = split(" ", $sString); // each entry in array $words is a word from the string
		$firstword = false;
		$sNewString = "";
		foreach($words AS $wordkey=>$word)
		{
			$word = trim($word); // just in case people double-space between sentences
			$lastchar = substr($word, -1); // $lastchar is used to determine if end-of-sentence is here
			if(($firstword) OR ($wordkey==0)) // if it's the start of sentence then we capitalize the word
			{
				$word = ucfirst($word);
				$firstword = false;
				$sNewString = $sNewString . " $word"; // add the word to the output string
			}
			elseif(($lastchar==".") OR($lastchar=="!") OR ($lastchar=="?")) // you can add more chars if you need to
			{
				$firstword = true; // now the next word will be first word of new sentence
				$sNewString = $sNewString . " $word"; // add the word to the output string
			}
			else
			{
				$sNewString = $sNewString . " $word"; // add the word to the output string
			}
		}
		$sNewString = trim($sNewString); // sometimes an extra space at beginning or end occurs, so this fixes it

		return $sNewString; // return the new string
	}

	// call it like this

	$badstring = "I LIKE TO EAT POTATO CHIPS. GO EAT POTATO CHIPS! WHERE ARE THE CHIPS?"; // example string
	print uc_sentences($badstring); // this will print "I like to eat potato chips. Go eat potato chips. Where are the potato chips?"
?>