7 files declare their use of Php in Drupal 8

ConfigEntityImportTest.php in core/modules/system/tests/src/Kernel/Entity/ConfigEntityImportTest.php

ConfigImportRenameValidationTest.php in core/tests/Drupal/KernelTests/Core/Config/ConfigImportRenameValidationTest.php

drupal-8.taxonomy-parent-multilingual-3066439.php in core/modules/system/tests/fixtures/update/drupal-8.taxonomy-parent-multilingual-3066439.php

Contains database additions to drupal-8.bare.standard.php.gz for testing the upgrade path of https://www.drupal.org/node/2455125.

drupal-8.views-taxonomy-parent-2543726.php in core/modules/system/tests/fixtures/update/drupal-8.views-taxonomy-parent-2543726.php

Contains database additions to drupal-8.bare.standard.php.gz for testing the upgrade path of https://www.drupal.org/node/2455125.

simpletest.module in core/modules/simpletest/simpletest.module

Provides testing functionality.

StorageComparerTest.php in core/tests/Drupal/Tests/Core/Config/StorageComparerTest.php

UuidTest.php in core/tests/Drupal/Tests/Component/Uuid/UuidTest.php