<?php

 /**

    * Copyright (c) 2005 Richard Heyes (http://www.phpguru.org/)

    *

    * All rights reserved.

    *

    * This script is free software.

    */



    /**

    * PHP5 Implementation of the Porter Stemmer algorithm. Certain elements

    * were borrowed from the (broken) implementation by Jon Abernathy.

    *

    * Usage:

    *

    *  $stem = PorterStemmer::Stem($word);

    *

    * How easy is that?

    */



	// Porter Stemmer

    class PorterStemmer

    {

        /**

        * Regex for matching a consonant

        * @var string

        */

        private static $regex_consonant = '(?:[bcdfghjklmnpqrstvwxz]|(?<=[aeiou])y|^y)';





        /**

        * Regex for matching a vowel

        * @var string

        */

        private static $regex_vowel = '(?:[aeiou]|(?<![aeiou])y)';





        /**

        * Stems a word. Simple huh?

        *

        * @param  string $word Word to stem

        * @return string       Stemmed word

        */

        public static function Stem($word)

        {

            if (strlen($word) <= 2) {

                return $word;

            }



            $word = self::step1ab($word);

            $word = self::step1c($word);

            $word = self::step2($word);

            $word = self::step3($word);

            $word = self::step4($word);

            $word = self::step5($word);



            return $word;

        }





        /**

        * Step 1

        */

        private static function step1ab($word)

        {

            // Part a

            if (substr($word, -1) == 's') {



                   self::replace($word, 'sses', 'ss')

                OR self::replace($word, 'ies', 'i')

                OR self::replace($word, 'ss', 'ss')

                OR self::replace($word, 's', '');

            }



            // Part b

            if (substr($word, -2, 1) != 'e' OR !self::replace($word, 'eed', 'ee', 0)) { // First rule

                $v = self::$regex_vowel;



                // ing and ed

                if (   preg_match("#$v+#", substr($word, 0, -3)) && self::replace($word, 'ing', '')

                    OR preg_match("#$v+#", substr($word, 0, -2)) && self::replace($word, 'ed', '')) { // Note use of && and OR, for precedence reasons



                    // If one of above two test successful

                    if (    !self::replace($word, 'at', 'ate')

                        AND !self::replace($word, 'bl', 'ble')

                        AND !self::replace($word, 'iz', 'ize')) {



                        // Double consonant ending

                        if (    self::doubleConsonant($word)

                            AND substr($word, -2) != 'll'

                            AND substr($word, -2) != 'ss'

                            AND substr($word, -2) != 'zz') {



                            $word = substr($word, 0, -1);



                        } else if (self::m($word) == 1 AND self::cvc($word)) {

                            $word .= 'e';

                        }

                    }

                }

            }



            return $word;

        }





        /**

        * Step 1c

        *

        * @param string $word Word to stem

        */

        private static function step1c($word)

        {

            $v = self::$regex_vowel;



            if (substr($word, -1) == 'y' && preg_match("#$v+#", substr($word, 0, -1))) {

                self::replace($word, 'y', 'i');

            }



            return $word;

        }





        /**

        * Step 2

        *

        * @param string $word Word to stem

        */

        private static function step2($word)

        {

            switch (substr($word, -2, 1)) {

                case 'a':

                       self::replace($word, 'ational', 'ate', 0)

                    OR self::replace($word, 'tional', 'tion', 0);

                    break;



                case 'c':

                       self::replace($word, 'enci', 'ence', 0)

                    OR self::replace($word, 'anci', 'ance', 0);

                    break;



                case 'e':

                    self::replace($word, 'izer', 'ize', 0);

                    break;



                case 'g':

                    self::replace($word, 'logi', 'log', 0);

                    break;



                case 'l':

                       self::replace($word, 'entli', 'ent', 0)

                    OR self::replace($word, 'ousli', 'ous', 0)

                    OR self::replace($word, 'alli', 'al', 0)

                    OR self::replace($word, 'bli', 'ble', 0)

                    OR self::replace($word, 'eli', 'e', 0);

                    break;



                case 'o':

                       self::replace($word, 'ization', 'ize', 0)

                    OR self::replace($word, 'ation', 'ate', 0)

                    OR self::replace($word, 'ator', 'ate', 0);

                    break;



                case 's':

                       self::replace($word, 'iveness', 'ive', 0)

                    OR self::replace($word, 'fulness', 'ful', 0)

                    OR self::replace($word, 'ousness', 'ous', 0)

                    OR self::replace($word, 'alism', 'al', 0);

                    break;



                case 't':

                       self::replace($word, 'biliti', 'ble', 0)

                    OR self::replace($word, 'aliti', 'al', 0)

                    OR self::replace($word, 'iviti', 'ive', 0);

                    break;

            }



            return $word;

        }





        /**

        * Step 3

        *

        * @param string $word String to stem

        */

        private static function step3($word)

        {

            switch (substr($word, -2, 1)) {

                case 'a':

                    self::replace($word, 'ical', 'ic', 0);

                    break;



                case 's':

                    self::replace($word, 'ness', '', 0);

                    break;



                case 't':

                       self::replace($word, 'icate', 'ic', 0)

                    OR self::replace($word, 'iciti', 'ic', 0);

                    break;



                case 'u':

                    self::replace($word, 'ful', '', 0);

                    break;



                case 'v':

                    self::replace($word, 'ative', '', 0);

                    break;



                case 'z':

                    self::replace($word, 'alize', 'al', 0);

                    break;

            }



            return $word;

        }





        /**

        * Step 4

        *

        * @param string $word Word to stem

        */

        private static function step4($word)

        {

            switch (substr($word, -2, 1)) {

                case 'a':

                    self::replace($word, 'al', '', 1);

                    break;



                case 'c':

                       self::replace($word, 'ance', '', 1)

                    OR self::replace($word, 'ence', '', 1);

                    break;



                case 'e':

                    self::replace($word, 'er', '', 1);

                    break;



                case 'i':

                    self::replace($word, 'ic', '', 1);

                    break;



                case 'l':

                       self::replace($word, 'able', '', 1)

                    OR self::replace($word, 'ible', '', 1);

                    break;



                case 'n':

                       self::replace($word, 'ant', '', 1)

                    OR self::replace($word, 'ement', '', 1)

                    OR self::replace($word, 'ment', '', 1)

                    OR self::replace($word, 'ent', '', 1);

                    break;



                case 'o':

                    if (substr($word, -4) == 'tion' OR substr($word, -4) == 'sion') {

                       self::replace($word, 'ion', '', 1);

                    } else {

                        self::replace($word, 'ou', '', 1);

                    }

                    break;



                case 's':

                    self::replace($word, 'ism', '', 1);

                    break;



                case 't':

                       self::replace($word, 'ate', '', 1)

                    OR self::replace($word, 'iti', '', 1);

                    break;



                case 'u':

                    self::replace($word, 'ous', '', 1);

                    break;



                case 'v':

                    self::replace($word, 'ive', '', 1);

                    break;



                case 'z':

                    self::replace($word, 'ize', '', 1);

                    break;

            }



            return $word;

        }





        /**

        * Step 5

        *

        * @param string $word Word to stem

        */

        private static function step5($word)

        {

            // Part a

            if (substr($word, -1) == 'e') {

                if (self::m(substr($word, 0, -1)) > 1) {

                    self::replace($word, 'e', '');



                } else if (self::m(substr($word, 0, -1)) == 1) {



                    if (!self::cvc(substr($word, 0, -1))) {

                        self::replace($word, 'e', '');

                    }

                }

            }



            // Part b

            if (self::m($word) > 1 AND self::doubleConsonant($word) AND substr($word, -1) == 'l') {

                $word = substr($word, 0, -1);

            }



            return $word;

        }





        /**

        * Replaces the first string with the second, at the end of the string. If third

        * arg is given, then the preceding string must match that m count at least.

        *

        * @param  string $str   String to check

        * @param  string $check Ending to check for

        * @param  string $repl  Replacement string

        * @param  int    $m     Optional minimum number of m() to meet

        * @return bool          Whether the $check string was at the end

        *                       of the $str string. True does not necessarily mean

        *                       that it was replaced.

        */

        private static function replace(&$str, $check, $repl, $m = null)

        {

            $len = 0 - strlen($check);



            if (substr($str, $len) == $check) {

                $substr = substr($str, 0, $len);

                if (is_null($m) OR self::m($substr) > $m) {

                    $str = $substr . $repl;

                }



                return true;

            }



            return false;

        }





        /**

        * What, you mean it's not obvious from the name?

        *

        * m() measures the number of consonant sequences in $str. if c is

        * a consonant sequence and v a vowel sequence, and <..> indicates arbitrary

        * presence,

        *

        * <c><v>       gives 0

        * <c>vc<v>     gives 1

        * <c>vcvc<v>   gives 2

        * <c>vcvcvc<v> gives 3

        *

        * @param  string $str The string to return the m count for

        * @return int         The m count

        */

        private static function m($str)

        {

            $c = self::$regex_consonant;

            $v = self::$regex_vowel;



            $str = preg_replace("#^$c+#", '', $str);

            $str = preg_replace("#$v+$#", '', $str);



            preg_match_all("#($v+$c+)#", $str, $matches);



            return count($matches[1]);

        }





        /**

        * Returns true/false as to whether the given string contains two

        * of the same consonant next to each other at the end of the string.

        *

        * @param  string $str String to check

        * @return bool        Result

        */

        private static function doubleConsonant($str)

        {

            $c = self::$regex_consonant;



            return preg_match("#$c{2}$#", $str, $matches) AND $matches[0]{0} == $matches[0]{1};

        }





        /**

        * Checks for ending CVC sequence where second C is not W, X or Y

        *

        * @param  string $str String to check

        * @return bool        Result

        */

        private static function cvc($str)

        {

            $c = self::$regex_consonant;

            $v = self::$regex_vowel;



            return     preg_match("#($c$v$c)$#", $str, $matches)

                   AND strlen($matches[1]) == 3

                   AND $matches[1]{2} != 'w'

                   AND $matches[1]{2} != 'x'

                   AND $matches[1]{2} != 'y';

        }

    }

?>