Convertir un string en chaine de mots clés

<?php
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/* Titre          : Convertir un string en chaine de mots clés                */
/*                                                                            */
/* URL            : http://www.phpsources.org/scripts610-PHP.htm              */
/* Auteur         : mercier133                                                */
/* Date édition   : 13 Oct 2010                                               */
/* Website auteur : http://www.servicesgratis.net                             */
/*                                                                            */
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/**
 * \brief Scinde une chaine de caractères en mots clés séparé par des virgules.
 * @param $str La chaine à analyser 
 */
function extractKeywords($str){
    // scinde la phrase grâce aux virgules et espacements + ;.:"'
    // ce qui inclus les " ", \r, \t, \n et \f
    $strArray = preg_split("/[\s,;\.\:\"\'\?\!]+/", $str);
    $return = "";
    if(count($strArray)>0){
        foreach($strArray as $s){
            if(!preg_match(
"/^([le|les|la|du|de|des|un|une|en|dans|dedans|[0-9]|ceci|cela|ce|se|ces|ses|" .
"ca|ça|tes|ta|ton])$/i", $s)){
                if(!empty($return)) $return.=",";
                $return.=$s;
            }
        }
    }
    return $return;
} 
?>