Fill out tracking location from a city lookup sometimes (just see comments)

lib/Tracking_USPS.lib.php

@@ -6,7 +6,7 @@ class Tracking_USPS {
      * Sometimes the API returns a city but no state or ZIP. This is a lookup table of city => state
      * so the API can return a more complete response.
      */
-    public $STATELESS_CITIES = [
+    public const STATELESS_CITIES = [
         "LOS ANGELES" => "CA",
         "NEW YORK" => "NY"
     ];
@@ -81,8 +81,8 @@ class Tracking_USPS {
          * Fill in state from list above when it's missing from the API response
          */
         if ($current_location->state == "" && $current_location->zip == "") {
-            if (in_array(strtoupper($current_location->city), $STATELESS_CITIES)) {
-                $current_location->state = $STATELESS_CITIES[$current_location->city];
+            if (array_key_exists(strtoupper($current_location->city), self::STATELESS_CITIES)) {
+                $current_location->state = self::STATELESS_CITIES[$current_location->city];
             }
         }
 
@@ -119,8 +119,8 @@ class Tracking_USPS {
              * Fill in state from list above when it's missing from the API response
              */
             if ($location->state == "" && $location->zip == "") {
-                if (in_array(strtoupper($location->city), $STATELESS_CITIES)) {
-                    $location->state = $STATELESS_CITIES[$location->city];
+                if (array_key_exists(strtoupper($location->city), self::STATELESS_CITIES)) {
+                    $location->state = self::STATELESS_CITIES[$location->city];
                 }
             }
             if ((empty($history->EventDate) || empty($history->EventTime)) && $i < count($trackinfo->TrackDetail) - 1) {