Function, we have introduced it in previous courses. The English name of function is: function, and the explanation of function has another meaning: function.
Function is function. Calling a function is calling a function.
We have also learned about some functions before, such as: is_int, phpinfo(), etc. We have introduced them all and they all have different functions. We won’t repeat it here.
Through the previous sentence, we can get several different rules:
After we understand, let’s explain the classification of functions. We divide functions into two categories: