<?php
/*
 * This file is part of Flarum.
 *
 * (c) Toby Zerner <toby.zerner@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Flarum\Api\Middleware;

use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use Zend\Stratigility\MiddlewareInterface;

class ReadJsonParameters implements MiddlewareInterface
{
    /**
     * {@inheritdoc}
     */
    public function __invoke(Request $request, Response $response, callable $out = null)
    {
        if (str_contains($request->getHeaderLine('content-type'), 'json')) {
            $input = json_decode($request->getBody(), true);
            
            if (! is_array($input)) {
                $input = [];
            }

            foreach ($input as $name => $value) {
                $request = $request->withAttribute($name, $value);
            }
        }

        return $out ? $out($request, $response) : $response;
    }
}

<?php
/*
 * This file is part of Flarum.
 *
 * (c) Toby Zerner <toby.zerner@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Flarum\Api\Middleware;

use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use Zend\Stratigility\MiddlewareInterface;

class ReadJsonParameters implements MiddlewareInterface
{
    /**
     * {@inheritdoc}
     */
    public function __invoke(Request $request, Response $response, callable $out = null)
    {
        if (str_contains($request->getHeaderLine('content-type'), 'json')) {
            $input = json_decode($request->getBody(), true);

            foreach ($input as $name => $value) {
                $request = $request->withAttribute($name, $value);
            }
        }

        return $out ? $out($request, $response) : $response;
    }
}

--- 
+++ 
@@ -23,6 +23,10 @@
     {
         if (str_contains($request->getHeaderLine('content-type'), 'json')) {
             $input = json_decode($request->getBody(), true);
+            
+            if (! is_array($input)) {
+                $input = [];
+            }
 
             foreach ($input as $name => $value) {
                 $request = $request->withAttribute($name, $value);
Make sure JSON request bodies are parsed as array.

Refs #533.