Merge branch '2.8' into 3.2

* 2.8:
  Fix optional cache warmers are always instantiated whereas they should be lazy-loaded
  add some \ on PHP_VERSION_ID for 2.8
  [PropertyInfo][DoctrineBridge] The bigint Doctrine's type must be converted to string

Tests/InlineTest.php

@@ -575,7 +575,7 @@ public function testParseTimestampAsDateTimeObject($yaml, $year, $month, $day, $
         $expected->setTimeZone(new \DateTimeZone('UTC'));
         $expected->setDate($year, $month, $day);
 
-        if (PHP_VERSION_ID >= 70100) {
+        if (\PHP_VERSION_ID >= 70100) {
             $expected->setTime($hour, $minute, $second, 1000000 * ($second - (int) $second));
         } else {
             $expected->setTime($hour, $minute, $second);
@@ -604,7 +604,7 @@ public function testParseNestedTimestampListAsDateTimeObject($yaml, $year, $mont
         $expected = new \DateTime($yaml);
         $expected->setTimeZone(new \DateTimeZone('UTC'));
         $expected->setDate($year, $month, $day);
-        if (PHP_VERSION_ID >= 70100) {
+        if (\PHP_VERSION_ID >= 70100) {
             $expected->setTime($hour, $minute, $second, 1000000 * ($second - (int) $second));
         } else {
             $expected->setTime($hour, $minute, $second);