Why isn't my script returning any values in Modelbuilder?

[LR2]

I want to output some variables for further use in ModelBuilder, however the parameters always end up empty. What's wrong?

[DanPatterson]

nothing is returned by the function, you could build up a msg, then use it as a return object to print when it exits the function

Also

GetMessages—ArcGIS Pro | Documentation

doe that appear anywhere in your script?

[LR2 · Accepted solution]

The message window from the modeler already shows everything at level 0. Returning values also doesn't work. However what does is 

    arcpy.SetParameter(2,PR_Out)
    arcpy.SetParameter(3,PID_Out)