How to redirect to search result page?
function MyModuleName_form_alter(&amp;$form, &amp;$form_state, $form_id)
{
   if ($form_id == 'search_form_id') {
     $form['#submit'][] = 'MyModuleName_custom_serch_form_submit';
   }  
} 

function MyModuleName_custom_serch_form_submit($form, &amp;$form_state)
{
  if(isset($_GET['q']) &amp;&amp; !empty($_GET['q']))
  {    
     $string_serch= $_GET['q'];
    drupal_goto("http://yourdomain.com/search?q=".$string_serch);
  }
}