Class to detect the user agent from the global var $_SERVER. Detects if is a bot, spider, crawler based on the HTTP_USER_AGENT and a list of web sniffers names or types.

UserAgentDetector.php

<?php

    /**
    * UserAgentDetector
    *
    * @author   Exadra37
    * @license  Free to use at your own risk. Provided as it is, without any warranty that will work for you.
    * @link     http://presta-hosting.com
    * @version  1.0.1
    * @since    v.1.0.0 - 09/03/2014
    *           v.1.0.1 - 09/03/2014 - fix typos
    * 
    */
    class UserAgentDetector
    {

        /**
         * $userAgent
         *     - name of the user agent if present in the global var $_SERVER
         *
         * @var mixed
         *
         * @access protected
         */
        protected $userAgent;

        /**
         * $crawlersNames
         *     - List of Crawler, bots, spiders
         *
         * @var string
         *
         * @access public
         */
        public $crawlersNames;

        /**
         * $botTypes
         *     - list of types of web sniffers like bot, crawl, spider and slurp
         *
         * @var string
         *
         * @access public
         */
        public $botTypes;

        public function __construct()
        {
            $this->userAgent = isset($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] : null;

            // List of Crawler, bots, spiders
            // Add man as you want from a online list, like this one:
            //  - http://www.robotstxt.org/db.html
            $this->crawlersNames = 'Google|msnbot|Rambler|Yahoo|AbachoBOT|accoona|
                AcioRobot|ASPSeek|CocoCrawler|Dumbot|FAST-WebCrawler|
                GeonaBot|Gigabot|Lycos|MSRBOT|Scooter|AltaVista|IDBot|eStyle|Scrubby';

            // List of web sniffers
            $this->botTypes = 'bot|crawl|slurp|spider';
        }

        /**
         * Detects if is a bot, spider, crawler based on the HTTP_USER_AGENT and a list of crawlers.
         *
         * Inspired in http://wanderr.com/jay/detect-crawlers-with-php-faster/2009/04/08/
         *
         * @author Exadra37
         *
         * @link   http://presta-hosting.com
         *
         * @return boolean                   - return true if is a bot, otherwise returns false.
         */
        public function isSpecificCrawler()
        {
            return !empty($this->userAgent) ? preg_match("/{$this->crawlersNames}/", $this->userAgent) > 0 : false;
        }

        /**
         * Simple detection to see if is a bot, spider, crawler or slurp based only on the HTTP_USER_AGENT.
         * 
         * Inspired in http://stackoverflow.com/a/15047834
         *
         * @author Exadra37
         *
         * @link   http://presta-hosting.com
         *
         * @return boolean                   - return true if is a bot, otherwise returns false.
         */
        public function isGenericBot()
        {
            return !empty($this->userAgent) ? preg_match("/{$this->botTypes}/", $this->userAgent) > 0 : false;
        }

        /**
         * Get the User Agent from the global var $_SERVER
         *
         * @author Exadra37
         *
         * @link   http://presta-hosting.com
         *
         * @return string                     - if isset returns user agent from global $_SERVER, otherwise returns null
         */
        public function getUserAgent()
        {
            return $this->userAgent;
        }
    }