diff --git a/src/ECharts.php b/src/ECharts.php
index 63421e1..e083433 100644
--- a/src/ECharts.php
+++ b/src/ECharts.php
@@ -146,9 +146,8 @@ private function quote($string)
      */
     public function getClientId()
     {
-        $id = $this->options['id'];
-
         if ($this->_clientId === null) {
+            $id = $this->options['id'];
             $this->_clientId = "echarts_{$id}";
         }