middleware.md

Middleware

Middleware is a config transformer which may be applied at run time over the config for a single class.

Getting config

Middleware are applied in order of creation during ->get() or ->exists() calls to config, each able to extend or modify config generated from prior middleware.

When requesting config, individual middleware may be disabled via the $excludeMiddleware flag, which is an int value (which may be assigned multiple int flags via bitwise |) which is passed as the second argument to the middlewares getClassConfig method.

true may be passed in as a global disable for all middleware.

Modifying config

Mutable methods such as ->set(), ->remove() or ->merge() always apply to the root config prior to middleware being applied.

Example middleware

Middleware could be used to implement common design patters such as config inheritance, caching, or decorators.

E.g. this is a middleware which adds extra data to class config

:::php
class ConfigExtender implements Middleware
{
    public function getClassConfig($class, $excludeMiddleware, $next)
    {
        // Get config from next middleware
        $config = $next($class, $excludeMiddleware);

        // Middlewares are responsible for self-disabling
        if ($excludeMiddleware === true || ($excludeMiddleware & self::DISABLE_FLAG)) {
            return $config;
        }

        // Merge config with extra data
        return array_merge($config, $this->getExtraConfig($class));
    }
}