View file phpBB3/config/default/routing/report.yml

phpbb_report_pm_controller:
    path:             /pm/{id}/report
    methods:          [GET, POST]
    defaults:
        _controller:  phpbb.report.controller:handle
        mode:         'pm'
    requirements:
        id:           \d+

phpbb_report_post_controller:
    path:             /post/{id}/report
    methods:          [GET, POST]
    defaults:
        _controller:  phpbb.report.controller:handle
        mode:         'post'
    requirements:
        id:           \d+