diff --git a/backend-php/api.php b/backend-php/api.php
index fa27072..0e282bb 100644
--- a/backend-php/api.php
+++ b/backend-php/api.php
@@ -210,7 +210,7 @@ CreateApi(function ($api) {
             // return only changes
             $content = json_decode($results[0]['content'], true);
             $has_full_rings = true;
-            foreach ($content as $idx => $item) {
+            foreach ($content as $_idx => $item) {
                 if (!isset($item['t-begin']) || !isset($item['t-end'])) {
                     $has_full_rings = false;
                     // optionally record $idx
@@ -225,7 +225,10 @@ CreateApi(function ($api) {
                 // without rings
                 $results = FastDBReq($db, "SELECT * FROM RINGS WHERE classId = ?", [$classId]);
                 $rings = json_decode(findClosestDateSort($results, $day)['content'], true);
-                $out = joinArraysByKey($content, $rings, true);
+                $out = $content;
+                if ($rings !== null) {
+                    $out = joinArraysByKey($content, $rings, true);
+                }
                 $db = null;
                 return ['data' => $out, 'type' => 1];
             }
@@ -238,7 +241,10 @@ CreateApi(function ($api) {
                 $schedule = json_decode(findClosestDateSort($results, $day)['content'], true);
                 $results = FastDBReq($db, "SELECT * FROM RINGS WHERE classId = ?", [$classId]);
                 $rings = json_decode(findClosestDateSort($results, $day)['content'], true);
-                $out = joinArraysByKey($schedule, $rings);
+                $out = $schedule;
+                if ($rings !== null) {
+                    $out = joinArraysByKey($schedule, $rings);
+                }
                 $db = null;
                 return ['data' => $out, 'type' => 0];
             } else {