title: Error on ldap auth with laravel
body: <p>I've followed the instructions at <a href="https://github.com/Adldap2/Adldap2-Laravel" rel="nofollow noreferrer">https://github.com/Adldap2/Adldap2-Laravel</a> with a brand new laravel project and I can't seem to get it to work. I have done the following:</p>
  
  <p>Added the following line to app.php</p>
  
  <pre><code>Adldap\Laravel\AdldapServiceProvider::class,
  Adldap\Laravel\AdldapAuthServiceProvider::class
  </code></pre>
  
  <p>Changed the driver to LDAP in auth.php</p>
  
  <pre><code>'users' =&gt; [
          'driver' =&gt; 'adldap',
          'model' =&gt; App\User::class,
      ],
  </code></pre>
  
  <p>However when I try to login I get the following error:</p>
  
  <pre><code>Use of undefined constant LDAP_OPT_PROTOCOL_VERSION - assumed 'LDAP_OPT_PROTOCOL_VERSION'
  </code></pre>