<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>

CC BY-SA 4.0
2020-12-08T07:19:51.530Z
thank you so much for the hint with the PHP versions, downgrading to PHP 7.4 was the solution :)
nerdess
CC BY-SA 4.0
2020-12-07T17:32:50.927Z
2020-12-07T17:32:50.927Z
Brad Bell
<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>

<craft3><installation>
Craft CMS throws Internal Server Error 500
# 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

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## 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 :)  

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