amphp/amp v3 compatibility

[abdullahseba]

The bundled AMP PHP adaptor is not compatible with APM V3 and causes an error when used. Amp server is listed as a dev dependency so maybe it should be version-locked until this is fixed?

[spawnia]

What is APM V3?

[abdullahseba]

Sorry, AMP v3*

[spawnia]

See #1262 (comment).

[abdullahseba]

If it's not being done now, the version should be locked to 2.x in composer.json?

[spawnia]

No, as it is an optional dependency.