Drush安装给出php错误

Question

[bootstrap.inc][1] [1]: https://i.stack.imgur.com/cnbLZ.png

Not sure what is going on here. It looks as if AccountInterface is already included in the boostrap.inc.

I tried updating the drush globaly and did get the latest version. In the local file however it still says I am on version 5.10.0. The composer.json within the local folder says I have it as 8.1. Thank you in advance!

vagrant@supersport:/var/www/drupalvm$ drush dl basic                                                                                                  

PHP Fatal error:  Class 'Drupal\Core\Session\AccountInterface' not found in 
/var/www/drupalvm/core/includes/bootstrap.inc on line 63                  
Drush command terminated abnormally due to an unrecoverable error.                                                                         
[error]    Error: Class 'Drupal\Core\Session\AccountInterface' not found in 
/var/www/drupalvm/core/includes/bootstrap.inc, line 63                                 

Answer 1

1. I renamed the original drush directory to something else (example: drush5) and then re-installed drush.

2. Deleted drush5 folder

3. I then got a seperate php error Error: Call to undefined function Drush\UpdateService\simplexml_load_file()
   Followed this link and ran sudo apt-get install php-xml