Answers.Body: <p>Based on the error message and this: <a href="https://php.watch/versions/8.0/deprecated-reflectionparameter-methods" rel="nofollow noreferrer">https://php.watch/versions/8.0/deprecated-reflectionparameter-methods</a>, it sounds like you're running PHP 8, which Craft isn't compatible with, yet.</p>
  <p>The soon-to-be-released Craft 3.6 adds PHP 8 compatibility, so you'll want to downgrade to PHP 7.4 until that's out.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-12-08T07:19:51.530Z
Answers.Text: thank you so much for the hint with the PHP versions, downgrading to PHP 7.4 was the solution :)
Answers.UserDisplayName: nerdess
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-12-07T17:32:50.927Z
Answers.LastActivityDate: 2020-12-07T17:32:50.927Z
Answers.UserDisplayName: Brad Bell
Body: <p>I got given a Craft CMS project build with composer and npm. Pointed valet to the correct folder, installed all the dependencies and started the app with <code>npm run watch</code>.</p>
  <p>http://localhost:3000 just gives me an &quot;Internal Server Error&quot; though...</p>
  <p><a href="https://i.sstatic.net/ipqSU.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ipqSU.png" alt="Craft CMS Internal Server Error" /></a></p>
  <p>There is nothing in the logs apart from sth inside storage/logs/web.log which does not sound like a showstopper:</p>
  <p><code>2020-12-07 06:59:06 [-][-][-][error][yii\base\ErrorException:8192] yii\base\ErrorException: Method ReflectionParameter::isArray() is deprecated in /vendor/yiisoft/yii2/web/Controller.php:133 Stack trace:</code></p>
  <p>Error 500 bugs are really hard to track down, any hints would be appreciated!</p>
  
Tags: <craft3><installation>
Title: Craft CMS throws Internal Server Error 500
ThreadText: # Craft CMS throws Internal Server Error 500
  
  (Asked by: username_0 on 2020-12-07)
  
  I got given a Craft CMS project build with composer and npm. Pointed valet to the correct folder, installed all the dependencies and started the app with `npm run watch`.
  
  http://localhost:3000 just gives me an "Internal Server Error" though...
  
  [![Craft CMS Internal Server Error](https://i.sstatic.net/ipqSU.png)](https://i.sstatic.net/ipqSU.png)
  
  There is nothing in the logs apart from sth inside storage/logs/web.log which does not sound like a showstopper:
  
  `2020-12-07 06:59:06 [-][-][-][error][yii\base\ErrorException:8192] yii\base\ErrorException: Method ReflectionParameter::isArray() is deprecated in /vendor/yiisoft/yii2/web/Controller.php:133 Stack trace:`
  
  Error 500 bugs are really hard to track down, any hints would be appreciated!
  
  **Tags:** craft3, installation
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2020-12-07. Score: 1 | Accepted answer
  
  Based on the error message and this: <https://php.watch/versions/8.0/deprecated-reflectionparameter-methods>, it sounds like you're running PHP 8, which Craft isn't compatible with, yet.
  
  The soon-to-be-released Craft 3.6 adds PHP 8 compatibility, so you'll want to downgrade to PHP 7.4 until that's out.
  
  > **Comments:**
  > **username_0**: thank you so much for the hint with the PHP versions, downgrading to PHP 7.4 was the solution :)  
  
  ---
  
  