Fixed GH-8730: DateTime::diff miscalculation is same time zone of different type

Author: derickr

ext/date/tests/gh8730.phpt

@@ -0,0 +1,28 @@
+--TEST--
+Bug GH-8730 (DateTime::diff miscalculation is same time zone of different type)
+--FILE--
+<?php
+$foo = new DateTime('2022-06-08 09:15:00', new DateTimeZone('-04:00'));
+$bar = new DateTime('2022-06-08 09:15:00', new DateTimeZone('US/Eastern'));
+print_r($foo->diff($bar));
+?>
+--EXPECT--
+DateInterval Object
+(
+    [y] => 0
+    [m] => 0
+    [d] => 0
+    [h] => 0
+    [i] => 0
+    [s] => 0
+    [f] => 0
+    [weekday] => 0
+    [weekday_behavior] => 0
+    [first_last_day_of] => 0
+    [invert] => 0
+    [days] => 0
+    [special_type] => 0
+    [special_amount] => 0
+    [have_weekday_relative] => 0
+    [have_special_relative] => 0
+)