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gyro/core/lib/components/referer.cls.php

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<?php
/**
 * Referer extends URL and adds some search engine recognition routines
 * 
 * @author Gerd Riesselmann
 * @ingroup Lib
 */
class Referer extends Url {
        private $keyword_query_key = false;
        private $original = '';

        /**
         * Constructor
         * 
         * @return Referer
         */
        public static function current() {
                $referer = Arr::get_item($_SERVER, 'HTTP_REFERER', '');
                return new Referer($referer);
        }
        
        /**
         * Create new Referer instancwe
         *
         * @param string $s_url
         * @return Referer
         */
        public static function create($s_url) {
                return new Referer($s_url);
        }
        
        /**
         * Constructor
         */
        public function __construct($referer_url = '') {
                $this->original = $referer_url;
                parent::__construct($referer_url);              
        }
        
        
        /**
         * Returns this query as a string
         *
         * The URL is not ready for outputting it on an HTML page, it must be HTMLescaped before! It is however URL escaped.
         * 
         * @return string This Url as a string.   
         * @exception Throws an exception if hostname is empty
         */
        public function build($mode = Url::ABSOLUTE, $encoding = Url::ENCODE_PARAMS) {
                if ($this->is_valid()) {
                        return parent::build($mode, $encoding);
                }
                return '';
        }
        
        
        /**
         * Returns original referer URL
         * 
         * @return string
         */
        public function get_original_referer_url() {
                return $this->original;
        }
        
        /**
         * Returns true if referer is internal
         */
        public function is_internal() {
                $url = Url::current();
                return ($this->get_host() == $url->get_host());
        }
        
        /**
         * Returns true if referer is external
         */
        public function is_external() {
                return (!$this->is_empty() && !$this->is_internal());
        }
        
        /**
         * Returns search engine information if referer is a search engine, else false 
         * 
         * Computation may be expensive, so handle with care.
         * 
         * Routine checks, if keywords are provided with referer, if not, referer is not recognized as a search engine!
         * 
         * @return mixed False if referer is no searchengine, an associateive array with fields 'domain', 'host', and 'keywords' otherwise 
         */
        public function search_engine_info() {
                if (!$this->is_external()) {
                        return false;
                }
                $query_params = $this->get_query_params();
                if (count($query_params) == 0) {
                        return false; // No params, no keywords...
                }

                $arr_se = $this->get_search_engines();
                $host = false; 
                // We are interested in search engines that provide a query only
                foreach($query_params as $query_param => $query_value) {
                        $possible_searchengine_sld = Arr::get_item($arr_se, $query_param, false);
                        if ($possible_searchengine_sld !== false) {
                                // We have a query param that *may* contain keywords
                                // depending on referer domain ('q' are keywords for google, but not for a Drupal page)
                                if (empty($host)) { 
                                        // Only parse host (expensive!) if needed
                                        $host = $this->parse_host(); 
                                }
                                if (in_array($host['sld'], $possible_searchengine_sld)) {               
                                        // We have a query parameter and a domain that belong to a search engine. Return
                                        return array(
                                                'domain' => $host['domain'],
                                                'searchengine' => $host['sld'],
                                                'host' => $this->get_host(),
                                                'keywords' => $query_value
                                        );
                                }
                        } 
                }
                        
                return false;
        }
                
        /**
         * Return array of keyword query keys and associated search engine second level domains
         */     
        private function get_search_engines() {
                return array (
                        'encquery' => array('aol'),
                        'p' => array('yahoo'),
                        'q' => array('google', 'msn', 'ask', 'altavista', 'alltheweb', 'gigablast', 'live', 'najdi', 'aol', 'club-internet', 'seznam', 'search', 'aolsvc', 't-online'),
                        'qs' => array('virgilio', 'alice'),
                        'qt' => array('looksmart'),
                        'query' => array('aol', 'lycos', 'cnn', 'mamma', 'mama'),
                        'rdata' => array('voila'),
                        's' => array('netscape'),
                        'terms' => array('about'),
                        'text' => array('yandex'),
                        'w' => array('seznam'),
                        'wd' => array('baidu')
                );
        }
}

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