laravel undefined index
Try this, it is worked for me, in following file:
vendor/laravel/framework/src/Illuminate/Foundation/PackageManifest.php
Find this line and comment it
$packages = json_decode($this->files->get($path), true);
Add two new lines after above commented line
$installed = json_decode($this->files->get($path), true);
$packages = $installed['packages'] ?? $installed;