define default values for additional config vars

src/Config/Configuration.php

@@ -14,8 +14,8 @@
 
 /**
  * Configuration can come from one or more of the following sources (from highest to lowest priority):
- * - values defined in php.ini
  * - environment variable (getenv, $_SERVER)
+ * - values defined in php.ini
  * - configuration file (todo)
  */
 class Configuration

src/Config/Defaults.php

@@ -119,4 +119,6 @@ interface Defaults
     public const OTEL_PHP_DISABLED_INSTRUMENTATIONS = [];
     public const OTEL_PHP_LOGS_PROCESSOR = 'batch';
     public const OTEL_PHP_LOG_DESTINATION = 'default';
+    public const OTEL_PHP_DEBUG_SCOPES_DISABLED = 'false';
+    public const OTEL_PHP_FIBERS_ENABLED = 'false';
 }

src/Context/Context.php

@@ -90,7 +90,7 @@ public function activate(): ScopeInterface
 
     private static function debugScopesDisabled(): bool
     {
-        return Configuration::getBoolean(Variables::OTEL_PHP_DEBUG_SCOPES_DISABLED, false);
+        return Configuration::getBoolean(Variables::OTEL_PHP_DEBUG_SCOPES_DISABLED);
     }
 
     public function withContextValue(ImplicitContextKeyedInterface $value): ContextInterface

src/Context/README.md

@@ -34,14 +34,14 @@ It is recommended to use a `try-finally` statement after `::activate()` to ensur
 ### Debug scopes
 
 By default, scopes created by `::activate()` warn on invalid and missing calls to `::detach()` in non-production
-environments. This feature can be disabled by setting the environment variable `OTEL_PHP_DEBUG_SCOPES_DISABLED` to a
-truthy value. Disabling is only recommended for applications using `exit` / `die` to prevent unavoidable notices.
+environments. This feature can be disabled by setting the environment variable `OTEL_PHP_DEBUG_SCOPES_DISABLED` to `true`.
+Disabling is only recommended for applications using `exit` / `die` to prevent unavoidable notices.
 
 ## Async applications
 
 ### Fiber support
 
-Requires `PHP >= 8.1`, an NTS build, `ext-ffi`, and setting the environment variable `OTEL_PHP_FIBERS_ENABLED` to a truthy value. Additionally `vendor/autoload.php` has to be preloaded for non-CLI SAPIs if [`ffi.enable`](https://www.php.net/manual/en/ffi.configuration.php#ini.ffi.enable) is set to `preload`.
+Requires `PHP >= 8.1`, an NTS build, `ext-ffi`, and setting the environment variable `OTEL_PHP_FIBERS_ENABLED` to `true`. Additionally `vendor/autoload.php` has to be preloaded for non-CLI SAPIs if [`ffi.enable`](https://www.php.net/manual/en/ffi.configuration.php#ini.ffi.enable) is set to `preload`.
 
 ### Event loops
 

src/Context/ZendObserverFiber.php

@@ -25,7 +25,7 @@ final class ZendObserverFiber
 {
     public static function isEnabled(): bool
     {
-        return Configuration::getBoolean(Variables::OTEL_PHP_FIBERS_ENABLED, false);
+        return Configuration::getBoolean(Variables::OTEL_PHP_FIBERS_ENABLED);
     }
 
     public static function init(): bool