Bugfixings in Config

- replaced usage of "!<unset>!" with null-returns
- fixed bool settings (0/1)
- fixed overriding config-values
- fixed basepath problems

src/Core/Config/Adapter/AbstractDbaConfigAdapter.php

@@ -6,7 +6,11 @@ use Friendica\Database\DBA;
 
 abstract class AbstractDbaConfigAdapter
 {
-	/** @var bool */
+	/**
+	 * The connection state of the adapter
+	 *
+	 * @var bool
+	 */
 	protected $connected = true;
 
 	public function __construct()
@@ -14,8 +18,66 @@ abstract class AbstractDbaConfigAdapter
 		$this->connected = DBA::connected();
 	}
 
+	/**
+	 * Checks if the adapter is currently connected
+	 *
+	 * @return bool
+	 */
 	public function isConnected()
 	{
 		return $this->connected;
 	}
+
+	/**
+	 * Formats a DB value to a config value
+	 * - null   = The db-value isn't set
+	 * - bool   = The db-value is either '0' or '1'
+	 * - array  = The db-value is a serialized array
+	 * - string = The db-value is a string
+	 *
+	 * Keep in mind that there aren't any numeric/integer config values in the database
+	 *
+	 * @param null|string $value
+	 *
+	 * @return null|array|string
+	 */
+	protected function toConfigValue($value)
+	{
+		if (!isset($value)) {
+			return null;
+		}
+
+		switch (true) {
+			// manage array value
+			case preg_match("|^a:[0-9]+:{.*}$|s", $value):
+				return unserialize($value);
+
+			default:
+				return $value;
+		}
+	}
+
+	/**
+	 * Formats a config value to a DB value (string)
+	 *
+	 * @param mixed $value
+	 *
+	 * @return string
+	 */
+	protected function toDbValue($value)
+	{
+		// if not set, save an empty string
+		if (!isset($value)) {
+			return '';
+		}
+
+		switch (true) {
+			// manage arrays
+			case is_array($value):
+				return serialize($value);
+
+			default:
+				return (string)$value;
+		}
+	}
 }