Basic text diff

function label_words($text) {
	$times_labeled = array();
	$words = explode(' ', $text);
	$new_words = array();
	for($i=0;$i<count($words);$i++) {
		if(isset($times_labeled[$words[$i]]))
			$times_labeled[$words[$i]]++;// = $times_labeled[$words[$i]]++;
		else
			$times_labeled[$words[$i]] = 0;
		$new_words[$times_labeled[$words[$i]] . '_' . $words[$i]] = '';
	}
	return $new_words;
}
 
function diff($text1, $text2) {
	$text1_words = label_words($text1);
	$text2_words = label_words($text2);
	$added_words = array_diff_key($text2_words, $text1_words);
	$removed_words = array_diff_key($text1_words, $text2_words);
	$text1_output = '';
	foreach($text1_words as $text1_word => $empty) {
		$original_word = substr($text1_word, strpos($text1_word, '_') + 1);
		$text1_output .= isset($removed_words[$text1_word]) ? "<del>$original_word</del> " : "$original_word ";
	}
	$text2_output = '';
	foreach($text2_words as $text2_word => $empty) {
		$original_word = substr($text2_word, strpos($text2_word, '_') + 1);
		$text2_output .= isset($added_words[$text2_word]) ? "<ins>$original_word</ins> " : "$original_word ";
	}
	return array($text1_output, $text2_output);
}