Reduce memory overhead of DatePeriod via virtual properties

Related to php#11644 and php#13988

Author: kocsismate

UPGRADING

@@ -1074,6 +1074,9 @@ PHP 8.4 UPGRADE NOTES
     of functions as well as serialization functions such as `json_encode()`,
     `serialize()`.
 
+- Date:
+  . Reduced memory usage of DatePeriod.
+
 - DOM:
   . The performance of DOMNode::C14N() is greatly improved for the case without
     an xpath query. This can give a time improvement of easily two order of

ext/date/php_date.stub.php

@@ -673,19 +673,40 @@ class DatePeriod implements IteratorAggregate
     /** @cvalue PHP_DATE_PERIOD_INCLUDE_END_DATE */
     public const int INCLUDE_END_DATE = UNKNOWN;
 
-    /** @readonly */
+    /**
+     * @readonly
+     * @virtual
+     */
     public ?DateTimeInterface $start;
-    /** @readonly */
+    /**
+     * @readonly
+     * @virtual
+     */
     public ?DateTimeInterface $current;
-    /** @readonly */
+    /**
+     * @readonly
+     * @virtual
+     */
     public ?DateTimeInterface $end;
-    /** @readonly */
+    /**
+     * @readonly
+     * @virtual
+     */
     public ?DateInterval $interval;
-    /** @readonly */
+    /**
+     * @readonly
+     * @virtual
+     */
     public int $recurrences;
-    /** @readonly */
+    /**
+     * @readonly
+     * @virtual
+     */
     public bool $include_start_date;
-    /** @readonly */
+    /**
+     * @readonly
+     * @virtual
+     */
     public bool $include_end_date;
 
     public static function createFromISO8601String(string $specification, int $options = 0): static {}