title: Magento addFieldToFilter: Two fields, match as OR, not AND
body: <p>I've been stuck on this for the last few hours. I got it working by hacking a few lines in <code>/lib/Varien/Data/Collection/Db.php</code>, but I'd rather use the proper solution and leave my core untouched.</p>
  
  <p>All I need to do is get a collection and filter it by two or more fields. Say, <code>customer_firstname</code> and <code>remote_ip</code>. Here's my (disfunctional without hacking <code>Db.php</code>) code:</p>
  
  <pre><code>$collection = Mage::getModel('sales/order')-&gt;getCollection()-&gt;
  addAttributeToSelect("*")-&gt;
  addFieldToFilter(array(array('remote_ip', array('eq'=&gt;'127.0.0.1')),
  array('customer_firstname', array('eq'=&gt;'gabe'))), array('eq'=&gt;array(1,2,3)));
  </code></pre>
  
  <p>With a stock <code>Db.php</code>, I tried this: (sample taken from <a href="http://magentoexpert.blogspot.com/2009/12/retrieve-products-with-specific.html" rel="noreferrer">http://magentoexpert.blogspot.com/2009/12/retrieve-products-with-specific.html</a>)</p>
  
  <pre><code>$collection-&gt;addFieldToFilter(array(
      array('name'=&gt;'orig_price','eq'=&gt;'Widget A'),
      array('name'=&gt;'orig_price','eq'=&gt;'Widget B'),           
  ));
  </code></pre>
  
  <p>But that gives me this error:</p>
  
  <pre><code>Warning: Illegal offset type in isset or empty  in magento/lib/Varien/Data/Collection/Db.php on line 369
  </code></pre>
  
  <p>If I wrap that with a try/catch, then it moves into _getConditionSql() and gives this error:</p>
  
  <pre><code>Warning: Invalid argument supplied for foreach()  in magento/lib/Varien/Data/Collection/Db.php on line 412
  </code></pre>
  
  <p>Does anyone have any working, functional code for doing this? I'm running Magento 1.9 (Enterprise). Thanks!</p>