diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index ae2f8915c3..9ede033ff9 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Config\BootstrapConfigStorageFactory;
+use Drupal\Core\Requirements;
 use Drupal\Core\Logger\RfcLogLevel;
 use Drupal\Core\Test\TestDatabase;
 use Drupal\Core\Session\AccountInterface;
@@ -20,9 +21,12 @@
 /**
  * Minimum supported version of PHP.
  *
- * Drupal cannot be installed on versions of PHP older than this version.
+ * @deprecated in Drupal 8.5.0, will be removed before Drupal 9.0.0. Use
+ *   \Drupal\Core\Requirements::DRUPAL_MINIMUM_PHP instead.
+ *
+ * @see https://www.drupal.org/node/2909361
  */
-const DRUPAL_MINIMUM_PHP = '5.5.9';
+const DRUPAL_MINIMUM_PHP = Requirements::MINIMUM_PHP;
 
 /**
  * Minimum recommended version of PHP.
@@ -39,8 +43,13 @@
  * 64M was chosen as a minimum requirement in order to allow for additional
  * contributed modules to be installed prior to hitting the limit. However,
  * 40M is the target for the Standard installation profile.
+ *
+ * @deprecated in Drupal 8.5.0, will be removed before Drupal 9.0.0. Use
+ *   \Drupal\Core\Requirements::DRUPAL_MINIMUM_PHP_MEMORY_LIMIT instead.
+ *
+ * @see https://www.drupal.org/node/2909361
  */
-const DRUPAL_MINIMUM_PHP_MEMORY_LIMIT = '64M';
+const DRUPAL_MINIMUM_PHP_MEMORY_LIMIT = Requirements::MINIMUM_PHP_MEMORY_LIMIT;
 
 /**
  * Error reporting level: display no errors.
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandler.php b/core/lib/Drupal/Core/Extension/ThemeHandler.php
index d54ff1fa1a..ce3dafe86c 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandler.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandler.php
@@ -3,6 +3,7 @@
 namespace Drupal\Core\Extension;
 
 use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Requirements;
 use Drupal\Core\State\StateInterface;
 
 /**
@@ -276,7 +277,7 @@ public function rebuildThemeData() {
       'description' => '',
       'features' => $this->defaultFeatures,
       'screenshot' => 'screenshot.png',
-      'php' => DRUPAL_MINIMUM_PHP,
+      'php' => Requirements::MINIMUM_PHP,
       'libraries' => [],
     ];
 
diff --git a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
index 8c105f25ae..36ba1d6a27 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
@@ -361,13 +361,3 @@ protected function systemListReset() {
   }
 
 }
-
-if (!defined('DRUPAL_EXTENSION_NAME_MAX_LENGTH')) {
-  define('DRUPAL_EXTENSION_NAME_MAX_LENGTH', 50);
-}
-if (!defined('DRUPAL_PHP_FUNCTION_PATTERN')) {
-  define('DRUPAL_PHP_FUNCTION_PATTERN', '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*');
-}
-if (!defined('DRUPAL_MINIMUM_PHP')) {
-  define('DRUPAL_MINIMUM_PHP', '5.3.10');
-}