diff --git a/model/SqlCriteria.php b/model/SqlCriteria.php
index 58b26dc..8e1accf 100644
--- a/model/SqlCriteria.php
+++ b/model/SqlCriteria.php
@@ -115,7 +115,7 @@ class SqlCriteria
     public function select($fields)
     {
         $fields = explode(',', $fields);
-        $this->select = $this->select + $fields;
+        $this->select = array_merge($this->select,$fields);
         return $this;
     }