docs PHP: add string SolrQuery::getHighlightQuery()

Author: omars44

docs/documentation.php

@@ -1666,6 +1666,14 @@ public function getFilterQueries() {}
      */
     public function getHighlight() {}
 
+    /**
+     * Returns hl.q param
+     *
+     * @return string
+     * @link http://docs.php.net/manual/en/solrquery.gethighlightquery.php
+     */
+    public function getHighlightQuery() {}
+
     /**
      * @param string $field_override [optional]
      *