title: PdoException when Updating composer, could not find driver
body: <p>I am trying to update php composer, but am receiving the error below:</p>
  
  <p>I attempted to fix it by installing pd_mysql, but that didn't work:</p>
  
  <pre><code>sudo apt-get install php5-gd php5-mysql
  </code></pre>
  
  <p>How can I update my composer?</p>
  
  <pre><code>jon@debian:~/NetBeansProjects/xxx$ php composer.phar update
  Loading composer repositories with package information
  Updating dependencies (including require-dev)
  Generating autoload files
  &gt; Incenteev\ParameterHandler\ScriptHandler::buildParameters
  Updating the "app/config/parameters.yml" file
  &gt; Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::buildBootstrap
  &gt; Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache
  
  
    [Doctrine\DBAL\Exception\DriverException]              
    An exception occured in driver: could not find driver  
  
  
  
    [Doctrine\DBAL\Driver\PDOException]  
    could not find driver                
  
  
  
    [PDOException]         
    could not find driver  
  
  
  Script Sensio\Bundle\DistributionBundle\Composer\ScriptHandler::clearCache handling the post-update-cmd event terminated with an exception
  
  
    [RuntimeException]                                                         
    An error occurred when executing the "'cache:clear --no-warmup'" command:  
  
      [Doctrine\DBAL\Exception\DriverException]                                
      An exception occured in driver: could not find driver                    
  
  
      [Doctrine\DBAL\Driver\PDOException]                                      
      could not find driver                                                    
  
  
      [PDOException]                                                           
      could not find driver                                                    
  
    .                                                                          
  
  
  update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock] [--no-custom-installers] [--no-autoloader] [--no-scripts] [--no-progress] [--with-dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--ignore-platform-reqs] [--prefer-stable] [--prefer-lowest] [-i|--interactive] [--root-reqs] [--] [&lt;packages&gt;]...
  </code></pre>