--- /dev/null
+<?php
+namespace Consolidation\Config\Util;
+
+/**
+ * Fetch a configuration value from a configuration group. If the
+ * desired configuration value is not found in the most specific
+ * group named, keep stepping up to the next parent group until a
+ * value is located.
+ *
+ * Given the following constructor inputs:
+ * - $prefix = "command."
+ * - $group = "foo.bar.baz"
+ * - $postfix = ".options."
+ * Then the `get` method will then consider, in order:
+ * - command.foo.bar.baz.options
+ * - command.foo.bar.options
+ * - command.foo.options
+ * If any of these contain an option for "$key", then return its value.
+ */
+class ConfigFallback extends ConfigGroup
+{
+ /**
+ * @inheritdoc
+ */
+ public function get($key)
+ {
+ return $this->getWithFallback($key, $this->group, $this->prefix, $this->postfix);
+ }
+
+ /**
+ * Fetch an option value from a given key, or, if that specific key does
+ * not contain a value, then consult various fallback options until a
+ * value is found.
+ *
+ */
+ protected function getWithFallback($key, $group, $prefix = '', $postfix = '.')
+ {
+ $configKey = "{$prefix}{$group}${postfix}{$key}";
+ if ($this->config->has($configKey)) {
+ return $this->config->get($configKey);
+ }
+ if ($this->config->hasDefault($configKey)) {
+ return $this->config->getDefault($configKey);
+ }
+ $moreGeneralGroupname = $this->moreGeneralGroupName($group);
+ if ($moreGeneralGroupname) {
+ return $this->getWithFallback($key, $moreGeneralGroupname, $prefix, $postfix);
+ }
+ return null;
+ }
+}