this里面的这个是什么意思?

class Java_Pagination
{
    protected $_total = 0;
    protected $_total_page = 0;
    protected $_page = 1;
    protected $_page_size = 10;
    protected $_link = '';
    protected $_grep = 3;
 
    protected $_admin = false;
    protected $_css_next = 'next-page';
    protected $_css_prev = 'prev-page';
    protected $_css_curr = 'curr-page';
    protected $_css_page = 'page-nav inline-block';
 
    public function __construct ( $page, $page_size, $total, $admin = false )
    {
        $this->set_current_page( $page );
        $this->set_page_size( $page_size );
        $this->set_total( $total );
 
        if ( $admin )
        {
            $this->_admin = $admin;
        }
        //$this->_link = $_SERVER['REQUEST_URI'];
        $this->set_link( $_SERVER['REQUEST_URI'] );
    }
    }

class Java_Pagination
{
    protected $_total = 0;
    protected $_total_page = 0;
    protected $_page = 1;
    protected $_page_size = 10;
    protected $_link = '';
    protected $_grep = 3;
 
    protected $_admin = false;
    protected $_css_next = 'next-page';
    protected $_css_prev = 'prev-page';
    protected $_css_curr = 'curr-page';
    protected $_css_page = 'page-nav inline-block';
 
    public function __construct ( $page, $page_size, $total, $admin = false )
    {
        $this->set_current_page( $page );
        $this->set_page_size( $page_size );
        $this->set_total( $total );
 
        if ( $admin )
        {
            $this->_admin = $admin;
        }
        //$this->_link = $_SERVER['REQUEST_URI'];
        $this->set_link( $_SERVER['REQUEST_URI'] );
    }
    }