Apache Solr Search proper syntax in url?
You should integrate Updated Apachesolr module. 
Write some custom menu hook to invoke your custom function.

 $query = apachesolr_current_query();
 $params_query = $query-&gt;getParams();


The above two statements will help us to check our solr queryString that we have triggered from our application.

/**
 * Implementation of hook_search_execute().
 */
function Custom_Function($keys = NULL, $conditions = NULL) {

  $filters = isset($conditions['fq']) ? $conditions['fq'] : array();
  $solrsort = isset($_GET['solrsort']) ? $_GET['solrsort'] : '';

  $response = NULL;
    $filt = array();
  // add custom filters if you want to add few custom filters in certain conditions.
   if($_GET['some key'] == 'some condition') {
        $filt[] = array('name' =&gt; 'entity_type', 'value' =&gt; 'trend_tips');
      }else{
        $filt[] = array('name' =&gt; 'im_16_field_category', 'value' =&gt; $_GET['category']);
      }
  $filters = $filt;
  $results = apachesolr_search_run('apachesolr', array('q' =&gt; $keys, 'fq' =&gt; $filters), $solrsort, 'search/' . arg(1), pager_find_page());

    // Set name for search results
    $query = apachesolr_current_query();

    $params_query = $query-&gt;getParams();

    if (module_hook($module, 'search_page')) {
      return module_invoke($module, 'search_page', $results); 
    }
 }
/**
 * Implementation of hook_apachesolr_query_prepare().
 */
function CustomeModule_apachesolr_query_prepare(&amp;$current_query) {

  // add query filters for Style tips and trends
  $current_query-&gt;addParam('fl', 'tm_image,tm_url,content');
  $current_query-&gt;addParam('qf', 'tm_title');
  $current_query-&gt;addParam('qf', 'tm_short_content');
  $current_query-&gt;addParam('qf', 'tm_perex');
  $current_query-&gt;addParam('mm', '1&lt;-90%'); // if you write more then 1 word to search, solr search as 'OR'
  $current_query-&gt;addParam('bf', 'recip(rord(created),4,5759,5759)^5.0'); // remove time dependency on search results


  // remove following content types (product and page) from search
    $current_query-&gt;addFilter('entity_type', 'product', true);
    $current_query-&gt;addFilter('bundle', 'page', true);
    $current_query-&gt;addFilter('tid', "63", true);
    $current_query-&gt;addFilter('tid', "64", true);


  $current_query-&gt;addParam('facet.field', 'bundle'); 
  // add a new facet type for filter trends and tips on search results

}


Please let me know if the above codebase helped to get some grip. 

Thanks