edit

src/Api.php

@@ -86,7 +86,7 @@ class Api
      *
      * @return mixed
      */
-    public function string($cate)
+    public function string($cate, $im = ',')
     {
         if ($cate) {
             $cate = explode(',', $cate);
@@ -94,7 +94,7 @@ class Api
             foreach ($cate as $k => $v) {
                 $result[$k] = $this->getName($v);
             }
-            return implode(',', $result);
+            return implode($im, $result);
         }
         return '';
     }