#3486021 PHP_IMAGE_VARIANT and PHP_IMAGE_TAG

Closes #3486021

includes/include.drupalci.hidden-variables.yml

@@ -256,6 +256,20 @@ variables:
   # Constrain Composer requirements to legacy major branch (Drupal 7).
   CONSTRAINT_CORE_LEGACY: "^7"
 
+  ################
+  # Pipeline configuration variables
+  ################
+
+  # The variant to use for Drupal 10+ within the definition of the image $_CONFIG_DOCKERHUB_ROOT/php-{PHP_VERSION}-{PHP_IMAGE_VARIANT}:{PHP_IMAGE_TAG}.
+  # 'ubuntu-apache' is the default, and 'apache' is the other possible value.
+  _TARGET_PHP_IMAGE_VARIANT: "ubuntu-apache"
+
+  # The variant to use for Drupal 7 within the definition of the image $_CONFIG_DOCKERHUB_ROOT/php-{PHP_VERSION}-{PHP_IMAGE_VARIANT}:{PHP_IMAGE_TAG}.
+  _TARGET_D7_PHP_IMAGE_VARIANT: "apache"
+
+  # The tag to use within the resulting image. Defaults to 'production' images.
+  _TARGET_PHP_IMAGE_TAG: "production"
+
   ################
   # Other
   ################