diff --git a/mod/data/field/checkbox/field.class.php b/mod/data/field/checkbox/field.class.php
index 25f0d5d24cd..3f47aa316ba 100644
--- a/mod/data/field/checkbox/field.class.php
+++ b/mod/data/field/checkbox/field.class.php
@@ -53,18 +53,16 @@ class data_field_checkbox extends data_field_base {
     }
 
     function display_add_field($recordid = 0, $formdata = null) {
-        global $CFG, $DB, $OUTPUT;
-
-        $content = array();
+        global $DB, $OUTPUT;
 
         if ($formdata) {
             $fieldname = 'field_' . $this->field->id;
-            $content = $formdata->$fieldname;
+            $content = $formdata->$fieldname ?? [];
         } else if ($recordid) {
-            $content = $DB->get_field('data_content', 'content', array('fieldid'=>$this->field->id, 'recordid'=>$recordid));
+            $content = $DB->get_field('data_content', 'content', ['fieldid' => $this->field->id, 'recordid' => $recordid]);
             $content = explode('##', $content);
         } else {
-            $content = array();
+            $content = [];
         }
 
         $str = '<div title="' . s($this->field->description) . '">';