Detect crawlers with PHP

I don’t know if anyone except me will need this script, so i put it in blog just not to loose it
Very simple function analyze $_SERVER[’HTTP_USER_AGENT’] variable and looking for crawler signature. If function founds crawler, it will return it’s name, otherwise – false.

Usage examples:
- save to database and output somethere in admin zone or on site
- save for indexing statistics and analyze it later
- use for cloacking or doorways :) ( i do not advise you to do it )

function crawlerDetect($USER_AGENT)
{
    $crawlers = array(
    array('Google', 'Google'),
    array('msnbot', 'MSN'),
    array('Rambler', 'Rambler'),
    array('Yahoo', 'Yahoo'),
    array('AbachoBOT', 'AbachoBOT'),
    array('accoona', 'Accoona'),
    array('AcoiRobot', 'AcoiRobot'),
    array('ASPSeek', 'ASPSeek'),
    array('CrocCrawler', 'CrocCrawler'),
    array('Dumbot', 'Dumbot'),
    array('FAST-WebCrawler', 'FAST-WebCrawler'),
    array('GeonaBot', 'GeonaBot'),
    array('Gigabot', 'Gigabot'),
    array('Lycos', 'Lycos spider'),
    array('MSRBOT', 'MSRBOT'),
    array('Scooter', 'Altavista robot'),
    array('AltaVista', 'Altavista robot'),
    array('IDBot', 'ID-Search Bot'),
    array('eStyle', 'eStyle Bot'),
    array('Scrubby', 'Scrubby robot')
    );

    foreach ($crawler as $c)
    {
        if (stristr($USER_AGENT, $c[0]))
        {
            return($c[1]);
        }
    }

    return false;
}

// example

$crawler = crawlerDetect($_SERVER['HTTP_USER_AGENT']);

if ($crawler )
{
   // it is crawler, it's name in $crawler variable
}
else
{
   // usual visitor
}

UPDATE:
After reading this i decide to update my code a bit. Change is connected to usage of function on high volume website.

<?php
  $crawlers = array(
    'Google'=>'Google',
    'MSN' => 'msnbot',
    'Rambler'=>'Rambler',
    'Yahoo'=> 'Yahoo',
    'AbachoBOT'=> 'AbachoBOT',
    'accoona'=> 'Accoona',
    'AcoiRobot'=> 'AcoiRobot',
    'ASPSeek'=> 'ASPSeek',
    'CrocCrawler'=> 'CrocCrawler',
    'Dumbot'=> 'Dumbot',
    'FAST-WebCrawler'=> 'FAST-WebCrawler',
    'GeonaBot'=> 'GeonaBot',
    'Gigabot'=> 'Gigabot',
    'Lycos spider'=> 'Lycos',
    'MSRBOT'=> 'MSRBOT',
    'Altavista robot'=> 'Scooter',
    'AltaVista robot'=> 'Altavista',
    'ID-Search Bot'=> 'IDBot',
    'eStyle Bot'=> 'eStyle',
    'Scrubby robot'=> 'Scrubby',
    );

function crawlerDetect($USER_AGENT)
{
    // to get crawlers string used in function uncomment it
    // it is better to save it in string than use implode every time
    // global $crawlers
    // $crawlers_agents = implode('|',$crawlers);
    $crawlers_agents = 'Google|msnbot|Rambler|Yahoo|AbachoBOT|accoona|AcioRobot|ASPSeek|CocoCrawler|Dumbot|FAST-WebCrawler|GeonaBot|Gigabot|Lycos|MSRBOT|Scooter|AltaVista|IDBot|eStyle|Scrubby';

    if ( strpos($crawlers_agents , $USER_AGENT) === false )
       return false;
    // crawler detected
    // you can use it to return its name
    /*
    else {
       return array_search($USER_AGENT, $crawlers);
    }
    */
}

// example

$crawler = crawlerDetect($_SERVER['HTTP_USER_AGENT']);

if ($crawler )
{
   // it is crawler, it's name in $crawler variable
}
else
{
   // usual visitor
}