forgot to - do和forgot doing區別

forget to do sth. 意思是忘記做某事了，這事沒做，forget doing sth.意思是忘記曾經做過某事，這事做了但不記得做過了。例句： Don't forget to lock the door when you leave. 你走時別忘了鎖門。

I forgot telling him about it， so I told him again.我忘了告訴過他這件事了，所以又和他説了一遍。