You are not allowed to access this file. Check app_dev.php for more information. about docker-symfony

[leroy0211]

app_dev is secured so localhost access only. Because you are running inside a docker, your own machine is not the localhost.
You have to allow your ip-address in the web/app_dev.php file in your symfony folder, or just remove the complete security in that file.

[unbelievableflavour]

Thanks, this and installing hp5-ctype and php5-dom extensions did the job

[unbelievableflavour]

Then i get the following error which also doesnt seem so normal.
RuntimeException in ClassCollectionLoader.php line 272: Failed to write cache file "/var/www/symfony/var/cache/dev/classes.php".

[B-Galati]

Just chmod 777 on your app/cache and app/log directory.
Better solutions are proposed on the doc here -> http://symfony.com/doc/current/setup/file_permissions.html

[eko]

Hello,

Thank you everyone for your help in this issue.

Closing this issue as it appears to be fixed now.