Automate Deployments with Git, Bitbucket and PHP

I'm in the process of trying to set up automatic deployments when I make a git push to my bitbucket repository. I have a php deploy script that I leveraged from http://brandonsummers.name/blog/2012/02/10/using-bitbucket-for-automated-deployments/ but when the script runs it is logging that it's only updating from a previous commit.

Here is an example. Let say I log into my server and type git pull. The server will update with the latest changes and lets say the hash for that commit was 001. However if I make serveral commits lets call them 002, 003, and 004 my script should run every time assuming I pushed those changes to bitbucket after every commit. The script runs but every time it will keep the changes from 001. Only when I log into my server and type git pull, will the server update to 004. Do you know what would cause this?

<?php

$ajax = true;
include('assets/init.inc.php');
// date_default_timezone_set('America/Los_Angeles');
// Also, this Class is not very secure...

$path = dirname(__FILE__);

class Deploy {

  /**
  * A callback function to call after the deploy has finished.
  * 
  * @var callback
  */
  public $post_deploy;
  
  /**
  * The name of the file that will be used for logging deployments. Set to 
  * FALSE to disable logging.
  * 
  * @var string
  */
  private $_log = 'deployments.log';

  /**
  * The timestamp format used for logging.
  * 
  * @link    http://www.php.net/manual/en/function.date.php
  * @var     string
  */
  private $_date_format = 'Y-m-d H:i:sP';

  /**
  * The name of the branch to pull from.
  * 
  * @var string
  */
  private $_branch = 'Master';

  /**
  * The name of the remote to pull from.
  * 
  * @var string
  */
  private $_remote = 'origin';

  /**
  * The directory where your website and git repository are located, can be 
  * a relative or absolute path
  * 
  * @var string
  */
  private $_directory;

  /**
  * The IP address from where BitBucket will be sending the IP address (Davey)
  * 
  * @var string
  */
  private $_ip = '63.246.22.222';
	
  /**
  * The IP address from where BitBucket will be sending the IP address (Davey)
  * 
  * @var string
  */
  private $_request_method = 'POST';
	
/**
  * Error variable for processing
  * 
  * @var bool
  */
  private $_error = false;
	
  /**
  * Sets up defaults.
  * 
  * @param  string  $directory  Directory where your website is located
  * @param  array   $data       Information about the deployment
  */
  public function __construct($directory, $options = array())
  {
    $this->log('Starting...');
	
    if (stripos($this->_request_method, $_SERVER['REQUEST_METHOD']) === false)
	{
	  $this->_error = true;
	  $this->log('Request method "'.$_SERVER['REQUEST_METHOD'].'" is not valid', 'ERROR');
	}
	else
	{
	  $this->log('Request method "'.$_SERVER['REQUEST_METHOD'].'": passed. Checking IP...');
	  
      if (!empty($_SERVER['REMOTE_ADDR']))
	  {
	    if (strlen($this->_ip) > 0) 
		{
          if (stripos($this->_ip, $_SERVER['REMOTE_ADDR']) !== false)
          {		  
            $this->log('IP "'.$_SERVER['REMOTE_ADDR'].'": passed. Continuing... ');
		  }
          else
          {
		    $this->_error = true;
            $this->log('This ip "'.$_SERVER['REMOTE_ADDR'].'" is not allowed', 'ERROR');
		  }
        }

        if ($this->_error !== true)
        {		
		
          // Determine the directory path
          $this->_directory = realpath($directory).DIRECTORY_SEPARATOR;
      
          $available_options = array('log', 'date_format', 'branch', 'remote');

          foreach ($options as $option => $value)
          {
              if (in_array($option, $available_options))
              {
                  $this->{'_'.$option} = $value;
              }  
          }

          $this->log('Attempting deployment...');
		}
	  }
	  else
	  {
	    $this->log('Missing REMOTE_ADDR', 'ERROR');
	  }
	}
  }

  /**
  * Writes a message to the log file.
  * 
  * @param  string  $message  The message to write
  * @param  string  $type     The type of log message (e.g. INFO, DEBUG, ERROR, etc.)
  */
  public function log($message, $type = 'INFO')
  {
      if ($this->_log)
      {
          // Set the name of the log file
          $filename = $this->_log;

          if ( ! file_exists($filename))
          {
              // Create the log file
              file_put_contents($filename, '');

              // Allow anyone to write to log files
              chmod($filename, 0666);
          }

          // Write the message into the log file
          // Format: time --- type: message
          file_put_contents($filename, date($this->_date_format).' --- '.$type.': '.$message.PHP_EOL, FILE_APPEND);
      }
  }

  /**
  * Executes the necessary commands to deploy the website.
  */
  public function execute()
  {
      try
      {
          // Make sure we're in the right directory
          exec('cd '.$this->_directory, $output);
          $this->log('Changing working directory... '.implode(' ', $output));

          // Discard any changes to tracked files since our last deploy
          exec('git reset --hard HEAD', $output);
          $this->log('Reseting repository... '.implode(' ', $output));

          // Update the local repository
          exec('git pull '.$this->_remote.' '.$this->_branch, $output);
          $this->log('Pulling in changes... '.implode(' ', $output));

          // Secure the .git directory
          exec('chmod -R og-rx .git');
          $this->log('Securing .git directory... ');

          if (is_callable($this->post_deploy))
          {
              call_user_func($this->post_deploy, $this->_data);
          }

          $this->log('Deployment successful.');
      }
      catch (Exception $e)
      {
          $this->log($e, 'ERROR');
      }
  }

}

// This is just an example
$deploy = new Deploy('/var/www/trekeffect.com/trekeffect.com');

// $deploy->post_deploy = function() use ($deploy) {
   // hit the wp-admin page to update any db changes
   // exec('curl http://www.foobar.com/wp-admin/upgrade.php?step=upgrade_db');
  // $deploy->log('Done.');
// };

// file_put_contents("{$GLOBALS['path']}/deployments.log", date('c'), FILE_APPEND);
$deploy->execute();

?>