diff --git a/core/modules/simpletest/src/InstallerTestBase.php b/core/modules/simpletest/src/InstallerTestBase.php
index 593f257a4d..96d98e05aa 100644
--- a/core/modules/simpletest/src/InstallerTestBase.php
+++ b/core/modules/simpletest/src/InstallerTestBase.php
@@ -261,6 +261,8 @@ protected function continueOnExpectedWarnings($expected_warnings = []) {
     // - etc.
     // We add one more selector than expected warnings to confirm that there
     // isn't any other warning before clicking the link.
+    // @todo Make this more reliable in
+    //   https://www.drupal.org/project/drupal/issues/2927345.
     $selectors = [];
     for ($i = 0; $i <= count($expected_warnings); $i++) {
       $selectors[] = 'h3#warning' . implode('', array_fill(0, $i + 1, '+details')) . ' summary';
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index c2390e0445..1f1227be66 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -160,8 +160,8 @@ function system_requirements($phase) {
   // Verify the user is running a supported PHP version.
   // If the site is running a recommended version of PHP, just display it
   // as an informational message on the status report. This will be overridden
-  // with an error or warning if the site is running a PHP version that is no
-  // longer supported by Drupal, or that will drop support in the near future.
+  // with an error or warning if the site is running older PHP versions for
+  // which Drupal has already or will soon drop support.
   $phpversion = $phpversion_label = phpversion();
   if (function_exists('phpinfo')) {
     // If the site is running a recommended PHP version and has the phpinfo()
@@ -185,13 +185,17 @@ function system_requirements($phase) {
       'severity' => REQUIREMENT_INFO,
     ];
   }
+
   if (version_compare($phpversion, DRUPAL_MINIMUM_PHP) < 0) {
     $requirements['php']['description'] = t('Your PHP installation is too old. Drupal requires at least PHP %version.', ['%version' => DRUPAL_MINIMUM_PHP]);
     $requirements['php']['severity'] = REQUIREMENT_ERROR;
     // If PHP is old, it's not safe to continue with the requirements check.
     return $requirements;
   }
-  elseif ((version_compare($phpversion, DRUPAL_RECOMMENDED_PHP) < 0) && ($phase === 'install' || $phase === 'runtime')) {
+  // @todo Warn about specific end dates for our PHP 5.5, 5.6, and 7.0 support
+  //   once each is set.
+  // @see https://www.drupal.org/project/drupal/issues/2927344
+  if ((version_compare($phpversion, DRUPAL_RECOMMENDED_PHP) < 0) && ($phase === 'install' || $phase === 'runtime')) {
     $requirements['php']['description'] = t('Your PHP installation is running version %version. It is recommended to upgrade to version %recommended or higher to ensure your site remains secure and continues to receive updates. See <a href="http://php.net/supported-versions.php">PHP\'s version support documentation</a> and the <a href=":php_requirements">PHP requirements handbook page</a> for more information.', ['%version' => $phpversion, '%recommended' => DRUPAL_RECOMMENDED_PHP, ':php_requirements' => 'https://www.drupal.org/docs/8/system-requirements/php']);
     $requirements['php']['severity'] = REQUIREMENT_WARNING;
   }