LIX - Swedish Readability Calculator

<?php
/**
 *    Läsbarhetsindex ( LIX )
 *    Swedish Readability Calculator
 *
 *    @author Kenth Hagström
 *    @version 1.0
 *    @license GPL
 *    @param $text string
 *    @param $periods array
**/
function lix( $text, $periods = array( '.', '!', '?', ':' ) )
{
    // Remove HTML tags from the text content
    $text = strip_tags( $text );

    // Get all words from the text and count 'em
    $all_words = str_word_count( $text, 2 );
    $total_words = count( $all_words );

    // Determine the number of sentences
    $total_sentences   = 0;
    foreach( $periods as $punctuation )
    {
        $total_sentences += substr_count( $text, $punctuation );
    }

    // Get the number of long words, ie words longer than 6 characters
    $long_words = 0;
    foreach( $all_words as $word )
    {
        if( strlen( $word ) > 6 )
        {
            $long_words++;
        }
    }

    // Some basic math, http://sv.wikipedia.org/wiki/LIX
    $average_sentence_length =  $total_words / $total_sentences;
    $part_long_words = 100 * ( $long_words / $total_words );
    $lix = $average_sentence_length + $part_long_words;

    return $lix;
}
?>