The specific usage of the second and three parameters of the is_callable function in php
When I was reading an open source code recently, I noticed that others set the second parameter to true when using the is_callable function. I wanted to know the specific meaning of the second parameter, so I read the manual later. There is also a third parameter, but I still don’t understand what the manual means. I hope friends who know more about it can give me some advice: 
