The first blog post: Why are the optional parameters in the PHP function prototype written this way? ,_PHP Tutorial

First blog post: Why are the optional parameters in the PHP function prototype written this way? ,

The first article is the beginning. Simply write something.

I just started learning PHP and encountered a problem when reading the PHP Manual: In the function prototype containing optional parameters, the optional parameters are not written in a clear way.

For example, explode function

<span>array explode ( string $delimiter , string $string [, int $limit ] )
</span>

Optional parameters are enclosed in "[square brackets]", then the third parameter $limit is an optional parameter.

But why not write it like this:

<span>array explode ( string $delimiter , string $string ,[int $limit ] )
</span>

I really can’t understand the position of this comma.