Fix leaks with multiple calls to DatePeriod iterator current()

Author: ndossche

ext/date/php_date.c

@@ -1606,6 +1606,11 @@ static zval *date_period_it_current_data(zend_object_iterator *iter)
 	timelib_time   *it_time = object->current;
 	php_date_obj   *newdateobj;
 
+	/* Not invalidated and object is immutable, so return the same object */
+	if (!Z_ISUNDEF(iterator->current)) {
+		return &iterator->current;
+	}
+
 	/* Create new object */
 	php_date_instantiate(get_base_date_class(object->start_ce), &iterator->current);
 	newdateobj = Z_PHPDATE_P(&iterator->current);

ext/date/tests/multiple_calls_date_period_iterator_current.phpt

@@ -0,0 +1,41 @@
+--TEST--
+Multiple calls to DatePeriod iterator current() leak objects
+--FILE--
+<?php
+$start = new DateTime('2018-12-31 00:00:00');
+$end   = new DateTime('2019-12-31 00:00:00');
+
+$interval = new DateInterval('P1M');
+$period = new DatePeriod($start, $interval, 1);
+
+$iter = $period->getIterator();
+var_dump($iter->current());
+var_dump($iter->current());
+var_dump($iter->current());
+
+?>
+--EXPECT--
+object(DateTime)#9 (3) {
+  ["date"]=>
+  string(26) "2018-12-31 00:00:00.000000"
+  ["timezone_type"]=>
+  int(3)
+  ["timezone"]=>
+  string(3) "UTC"
+}
+object(DateTime)#9 (3) {
+  ["date"]=>
+  string(26) "2018-12-31 00:00:00.000000"
+  ["timezone_type"]=>
+  int(3)
+  ["timezone"]=>
+  string(3) "UTC"
+}
+object(DateTime)#9 (3) {
+  ["date"]=>
+  string(26) "2018-12-31 00:00:00.000000"
+  ["timezone_type"]=>
+  int(3)
+  ["timezone"]=>
+  string(3) "UTC"
+}