In short ... that's not true. We can argue about memory consumption, data-structures etc ... but node and python are memory whores as well if we compare them to strong and static typed languages.
PHP can scale it just sucks at certain operations or applications. a message queue in PHP is possible, I wrote one with ticks and sockets, process forking and everything ... I just don't think it's nice to use and for what it does it's rather inefficient in comparison to go or node.
calculations are a pain, the memory consumption is sub-optimal but lets not forget the meaning of a dynamic and weak typed language with runtime type cohesions, as well as that those problems apply to every language within this domain.
I will not go into this any further because I think there will come some more concrete answers just don't forget people often confuse different types of efficiency. Often the boundaries of scaling are based on the implementation and architecture not the initial language the application is written in.
.... you can f*ck up in any language.