track-referrer-keyword.php

<?php

function get_keyword($referer)
{
    $search_phrase = '';
    $engines = array('dmoz'     => 'q=',
                     'aol'      => 'q=',
                     'ask'      => 'q=',
                     'google'   => 'q=',
                     'bing'     => 'q=',
                     'hotbot'   => 'q=',
                     'teoma'    => 'q=',
                     'yahoo'    => 'p=',
                     'altavista'=> 'p=',
                     'lycos'    => 'query=',
                     'kanoodle' => 'query='
                     );
 
    foreach($engines as $engine => $query_param) {
        // Check if the referer is a search engine from our list.
        // Also check if the query parameter is valid.
        if (strpos($referer, $engine.".") !==  false && 
            strpos($referer, $query_param) !==  false) {
 
            // Grab the keyword from the referer url
            $referer .= "&";
            $pattern = "/[?&]{$query_param}(.*?)&/si";
            preg_match($pattern, $referer, $matches);
            $search_phrase = urldecode($matches[1]);
            return array($engine, $search_phrase);
        }   
    }
    return;
}

function get_referrer($my_site) {
    /* If the referrer is from outside the domain, store the url in a session */
if(!substr($_SERVER['HTTP_REFERER'], 0, strlen($my_site)) !== $my_site) {
    return $_SERVER['HTTP_REFERER'];
} 


?>