<?php
    #
    # An implementation of the Porter Stemming Algorithm in PHP
    # ( see http://www.tartarus.org/~martin/PorterStemmer/ )
    #
    # (C)2005 Cal Henderson, <cal@iamcal.com>
    #
    # usage:   $stem = Porter_Stemmer::stem($word);
    #


    #
    # PHP4 doesn't have class variables, so we'll use the GLOBALS stash
    #

    $GLOBALS['Porter_Stemmer_step2list'] = array(
        'ational'=>'ate',
        'tional'=>'tion',
        'enci'=>'ence',
        'anci'=>'ance',
        'izer'=>'ize',
        'bli'=>'ble',
        'alli'=>'al',
        'entli'=>'ent',
        'eli'=>'e',
        'ousli'=>'ous',
        'ization'=>'ize',
        'ation'=>'ate',
        'ator'=>'ate',
        'alism'=>'al',
        'iveness'=>'ive',
        'fulness'=>'ful',
        'ousness'=>'ous',
        'aliti'=>'al',
        'iviti'=>'ive',
        'biliti'=>'ble',
        'logi'=>'log'
    );

    $GLOBALS['Porter_Stemmer_step3list'] = array(
        'icate'=>'ic',
        'ative'=>'',
        'alize'=>'al',
        'iciti'=>'ic',
        'ical'=>'ic',
        'ful'=>'',
        'ness'=>''
    );

    $GLOBALS['Porter_Stemmer_r'] = array(
        'c'    => '[^aeiou]',            # consonant
        'v'    => '[aeiouy]',            # vowel
        'c2'    => '[^aeiou][^aeiouy]*',    # consonant sequence
        'v2'    => '[aeiouy][aeiou]*',        # vowel sequence

        'mgr0'    => '^([^aeiou][^aeiouy]*)?[aeiouy][aeiou]*[^aeiou][^aeiouy]*',                        # [C]VC... is m>0
        'meq1'    => '^([^aeiou][^aeiouy]*)?[aeiouy][aeiou]*[^aeiou][^aeiouy]*([aeiouy][aeiou]*)?$',            # [C]VC[V] is m=1
        'mgr1'    => '^([^aeiou][^aeiouy]*)?[aeiouy][aeiou]*[^aeiou][^aeiouy]*[aeiouy][aeiou]*[^aeiou][^aeiouy]*',    # [C]VC[V] is m=1
        '_v'    => '^([^aeiou][^aeiouy]*)?[aeiouy]',                                    # vowel in stem
    );


    #
    # the class really just puts the method in a namespace
    #

    class Porter_Stemmer {

        #
        # utility function to chop {x} chars from the end of a string
        #

        function end_chop($str, $len){
            return substr($str, 0, strlen($str)-$len);
        }

        #
        # the meat is here
        #

        function stem($w){

            # load into scope
            $r =& $GLOBALS['Porter_Stemmer_r'];
            $step2list =& $GLOBALS['Porter_Stemmer_step2list'];
            $step3list =& $GLOBALS['Porter_Stemmer_step3list'];


            $w = StrToLower($w);

            #
            # length at least 3
            #

            if (strlen($w) < 3) {
                return $w;
            }

            #
            # now map initial y to Y so that the patterns never treat it as vowel:
            #

            $firstch = substr($w, 0, 1);

            if ($firstch == 'y') {
                $w = ucfirst($w);
            }

            #
            # Step 1a
            #

            if (preg_match('/(ss|i)es$/', $w)){
                $w = Porter_Stemmer::end_chop($w, 2);
            }

            else if (preg_match('/([^s])s$/', $w)){
                $w = Porter_Stemmer::end_chop($w, 1);
            }

            #
            # Step 1b
            #

            if (preg_match('/eed$/', $w)) {
                $pre = Porter_Stemmer::end_chop($w, 3);

                if (preg_match("/$r[mgr0]/", $pre)) {
                    $w = Porter_Stemmer::end_chop($w, 1);
                }
            }

            else if (preg_match('/(ed|ing)$/', $w, $m1)){

                $stem = Porter_Stemmer::end_chop($w, strlen($m1[1]));

                if (preg_match("/$r[_v]/", $stem)){

                    $w = $stem;

                    if (preg_match('/(at|bl|iz)$/', $w)) {
                        $w .= "e";
                    }

                    else if (preg_match('/([^aeiouylsz])\1$/', $w)) {
                        $w = Porter_Stemmer::end_chop($w, 1);
                    }

                    else if (preg_match("/^$r[c2]$r[v][^aeiouwxy]$/", $w)) {
                        $w .= "e";
                    }
                }
            }

            #
            # Step 1c
            #

            if (preg_match('/y$/', $w)) {

                $stem = Porter_Stemmer::end_chop($w, 1);

                if (preg_match("/$r[_v]/", $stem)){

                    $w = $stem."i";
                }
            }

            #
            # Step 2
            #

            if (preg_match('/(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$/', $w, $m1)){

                $suffix = $m1[1];
                $stem = Porter_Stemmer::end_chop($w, strlen($suffix));

                if (preg_match("/$r[mgr0]/", $stem)) {
                    $w = $stem . $step2list[$suffix];
                }
            }

            #
            # Step 3
            #

            if (preg_match('/(icate|ative|alize|iciti|ical|ful|ness)$/', $w, $m1)){

                $suffix = $m1[1];
                $stem = Porter_Stemmer::end_chop($w, strlen($suffix));

                if (preg_match("/$r[mgr0]/", $stem)) {
                    $w = $stem . $step3list[$suffix];
                }
            }

            #
            # Step 4
            #

            if (preg_match('/(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$/', $w, $m1)){

                $stem = Porter_Stemmer::end_chop($w, strlen($m1[1]));

                if (preg_match("/$r[mgr1]/", $stem)) {
                    $w = $stem;
                }
            }

            else if (preg_match('/(s|t)(ion)$/', $w, $m1)){

                $stem = Porter_Stemmer::end_chop($w, strlen($m1[2]));

                if (preg_match("/$r[mgr1]/", $stem)) {
                    $w = $stem;
                }
            }

            #
            #  Step 5
            #

            if (preg_match('/e$/', $w)) {

                $stem = Porter_Stemmer::end_chop($w, 1);

                $b1 = preg_match("/$r[mgr1]/", $stem);
                $b2 = preg_match("/$r[meq1]/", $stem);
                $b3 = preg_match("/^$r[c2]$r[v][^aeiouwxy]$/", $stem);

                if ($b1 || ($b2 && !$b3)) {
                    $w = $stem;
                }
            }

            if (preg_match('/ll$/', $w) && preg_match("/$r[mgr1]/", $w)) {
                $w = Porter_Stemmer::end_chop($w, 1);
            }


            #
            # and turn initial Y back to y
            #

            if ($firstch == 'y') {
                $w = lcfirst($w);
            }

            return $w;
        }

    }

?>