title: Empty string instead of null values Eloquent
body: <p>I'm trying to create entities using mass-assignment Eloquent feature...</p>
  
  <pre><code>$new = new Contact(Input::all());
  $new-&gt;save();
  </code></pre>
  
  <p>The problem's that this way, every field's filled out with an empty string instead of <code>null</code> values as I expected.</p>
  
  <p>I'm currently developing the system and still some table columns're not defined, that's why using this method, to avoid adding every new field to <code>$fillable</code> array and to a <code>new Contact(array(...));</code>...</p>
  
  <p>Also I've around 20 fields in this table, so It'd be a bit ugly to have an array such as</p>
  
  <pre><code>$new = new Contact(array(
      'salutation' =&gt; Input::get('salutation'),
      'first_name' =&gt; Input::get('first_name'),
      'last_name'  =&gt; Input::get('last_name'),
      'company_id' =&gt; Input::get('company_id'),
      'city' =&gt; ...
      ...
  ));
  </code></pre>
  
  <p>Any tips of how to do this or fix?</p>
  
  <p><strong>Update</strong> By now I've sorted out this doing the array_filter in the <code>App::before()</code> filter.</p>
  
  <p><strong>Update</strong> In filter was a bit mess. I end up doing:</p>
  
  <pre><code>public static function allEmptyIdsToNull()
  {
      $input = Input::all();
  
      $result = preg_grep_keys ( '/_id$/' , $input );
  
      $nulledResults = array_map(function($item) {
          if (empty($item))
              return null;
  
          return $item;
      }, $result);
  
      return array_merge($input, $nulledResults);
  }
  </code></pre>
  
  <p>And in my functions.php.</p>
  
  <pre><code>if ( ! function_exists('preg_grep_keys'))
  {
      /**
      * This function gets does the same as preg_grep but applies the regex
      * to the array keys instead to the array values as this last does.
      * Returns an array containing only the keys that match the exp.
      * 
      * @author Daniel Klein
      * 
      * @param  string  $pattern
      * @param  array  $input
      * @param  integer $flags
      * @return array
      */
      function preg_grep_keys($pattern, array $input, $flags = 0) {
          return array_intersect_key($input, array_flip(preg_grep($pattern, array_keys($input), $flags)));
      }
  }
  </code></pre>
  
  <p>By now only working with fields that ends with "_id". This is my biggest problem as if a relationship is not <code>NULL</code>, the database will throw an error as the foreign key "" cannot be found.</p>
  
  <p>Works perfect. Any comment?</p>