为什么带下划线的变量可以在php中没有下划线的情况下读取？

Question

I have saw too many php class example use the code like this:

<?php
class Test
{
    public $_default = array(
      'page' => 1,
      'perPage' => 10 
    );

    public function __construct()
    {
      $curPage = $this->default['page'];
      $perPage = $this->default['perPage'];
    }
}

Why can $_default be used via $this->default instead of $this->_default ?

And which one is recommended?

P.S. If this question is duplicate, please tell me and I will delete it as soon as possible.

Answer 1

Private class members are preceded by a single underscore.

For more info:

http://pear.php.net/manual/en/standards.naming.php