为什么下划线（_）用于php codeigniter中的函数_save_cart等函数？

Question

I saw many tutorials underscores (_) are used in function.

But I don't know why it is used and how can I use ?

Like this :

function _save_cart()
{

}

Answer 1

In objective languages functions and variables names seperate with capitalize char, forexample: saveCart(), getCart(), ...

But in functional languages people use underscore and i think it comes from C posix standarts/notations.

C language doesn't support private and protected keywords so people generally use one or two underscore as pre extension for make the function private or protected.

Php firstly created as a functional language after a long time ZEND added object oriented features. So many people used to write it like a functional language. And so if you see a function like _save_cart you can understand that: an old school php coder make this function protected or private with posix way.