How to send a private message to a VK user from an iframe application?

Question

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There is a VK API method - messages.send. Actually, he sends a personal message to the user. However, the method is only available for standalone applications. It doesn't seem to work for Iframe (at least I couldn't run it).
So the question is, how can I send a private message to the user from the iframe application?

Answer 1

This method can be called with a user access key obtained in the Standalone application via Implicit Flow. Permissions required: messages.
This method can be called with a community access key. Permissions required: messages .
messages - Access to advanced methods for working with messages ( only for Standalone applications ).

Answer 2

Necroposting:
Make a php script that will take a get parameter containing the user id and send a message to this id. In this case, in the php script it will be enough to use the community access key, which can be created in the community settings in the api section.
Well, then just from your iframe make a get request for this script with the corresponding user id.