Catching Keywords from Search Engines

Question

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With this class we try to catch some keywords from google, yahoo and bing search engines.

<?php
class keywords
{
 private $referer;
 private $_e;
 public $keywords;

 public function __construct()
 {
   if($_SERVER['HTTP_REFERER'])
   {
     if(preg_match("#\.google|search\.yahoo|\.bing#", $_SERVER['HTTP_REFERER']))
     {
       $this->referer = urldecode($_SERVER['HTTP_REFERER']);
     }
     else
     {
       return;
     }    
   }
   else
   {
     return;
   }    
 }

 private function getSeparators()
 {
   $this->_e = (preg_match("#\?q=|\?p=#", $this->referer)) ? "\?" : "&";
 }

 public function getKeywords()
 {
   if(!empty($this->referer))
   {
     $this->getSeparators();
     //google
     if(preg_match("#\.google#", $this->referer))
     {
       $m_ = preg_match("#{$this->_e}q=(.+?)&#si", $this->referer, $this->keywords);

       if($m_ == 0)
       {
         return false;
       }
     }
     //yahoo
     elseif(preg_match("#search\.yahoo#", $this->referer))
     {
       $m_ = preg_match("#{$this->_e}p=(.+?)\&#si", $this->referer, $this->keywords);

       if($m_ == 0)
       {
         return false;
       }
     }
     //bing
     elseif(preg_match("#\.bing#", $this->referer))
     {
       $m_ = preg_match("#{$this->_e}q=(.+?)\&#si", $this->referer, $this->keywords);

       if($m_ == 0)
       {
         return false;
       }
     }
     else
     {
       return false;
     }

     return $this->keywords[1];
   }
   else
   {
     return false;
   }
  }
}
?>

Save this script as keywords_class.php

Now let’s try to print these keywords.

<?php
require_once('keywords_class.php');
$keywordsObj = new keywords();
$keys = $keywordsObj->getKeywords();

if($keys)
{
 print $keys;
}
else
{
 print "ooops";
}
?>

Save this code as index.php

Posted 18-Dec-09 1:33am

caprico.caprico

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1 solution

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

fly904 · Answer 1 · 2010-01-22T09:16:00

There is a bug with your regex.
Say for example that you were refered to by google.uk/search?q=example&ie=utf-8, your code would return 'example'. If, however, you were refered to by google.uk/search?q=example, it would return 'oops'.

The simple fix is to change the limitation variable from & to (&|$).

The following is the testbed I used.

PHP

<?php
class SearchEngineKeywords
{
    private $referer;

    public function __construct( $search_string = null )
    {
        $referer = isset( $search_string ) && is_string( $search_string )
            ? $search_string : ( isset( $_SERVER[ 'HTTP_REFERER' ] )
                ? $_SERVER[ 'HTTP_REFERER' ] : null );

        if ( isset( $referer ) && preg_match( '/\.google|search\.yahoo|\.bing/' , $referer ) )
            $this->referer = urldecode( $referer );
    }

    public function get_keywords()
    {
        if ( !isset( $this->referer ) )
            return false;

        // Google and Bing
        if ( preg_match( '/\.google|\.bing/' , $this->referer ) )
            $get_variable_name = 'q';

        // Yahoo
        elseif( preg_match( '/search\.yahoo/', $this->referer ) )
            $get_variable_name = 'p';

        // Default
        else
            return false;

        return preg_match( '/' . $this->get_separators() . $get_variable_name . '=(.+?)(&|$)/si' , $this->referer , $keywords ) == 0
            ? false : $keywords[1];
    }

    private function get_separators()
    {
        return preg_match( '/\?q=|\?p=/' , $this->referer ) ? '\?' : '&';
    }
}
?>

The previous code was tested by:

PHP

<?php
$SearchEngineKeywords = new SearchEngineKeywords( 'http://www.google.co.uk/search?q=example' );

if ( $keywords = $SearchEngineKeywords->get_keywords() )
{
	echo $keywords;
}
else
{
	echo 'ooops';
}
?>