Message in Phpstorm
_Problems found loading plugins: Plugin "Symfony Plugin" was not loaded: required plugin "de.espend.idea.php.annotation" not installed._
In description of symfony plugin:
_(Optional) Install PHP Annotations_
Is it optional or required?
looks like required because installing PHP Annotations fixed the problem for me
@shvrcho thank you, @metaer I confirm it's working also for me :).
Yes, It works after installing PHP Annotations
If it is required - may be it need to be fixed in the plugin description:

If it is optional - this issue is a bug.
In any case, thanks for this plugin
According to the release notes for v0.14.143
- Move PHP Annotation plugin
de.espend.idea.php.annotationfrom soft to hard dependency to drop duplicate code usages #448
I would say the PHP Annotations isn't optional any longer, so the Install documentation should be changed. Fixed by 55957c7, going to be released with 0.14.145.
Reinstalling the plugin automatically adds the dependency, after asking for confirmation, so for new installations it will work as well.
For existing installations there should be a more concise hint, that the Annotations plugin must be installed.
On the other hand, it would be a nice feature of the IDEA platform to resolve a plugin's dependencies automatically on its update. I believe aside the documentation, this is the major pain of this issue.
I'd say, this issue is solved and can be closed.
I have the same problem even after reinstalling the plugin.
PhpStorm 2018.1 EAP
Build #PS-181.3494.16, built on February 7, 2018
@matiux please check Haehnchen/idea-php-annotation-plugin#105
Most helpful comment
looks like required because installing PHP Annotations fixed the problem for me