在另一个类中的类

Question

I am new to PHP OOP and would like to try to nest several classes within another class, to latter call them like so:

$sql = new SQL();
$sql->Head()->Description($_SESSION['page']);
  //OR
$sql->Head()->Keywords($_SESSION['page'])
  //OR
$sql->Body()->Clients($_SESSION['client'])
  //ETC
$query = $sql->Run(); // equivalent to mysql_query("...");

As you can guess, I run into some problems and ended with this poor code:

<?php
require( $_SERVER['DOCUMENT_ROOT'] . '/#some_db_directory/database.php');
//This file contains $db['host'], $db['user'], etc...

class SQL {
    public $sql;

    public function __construct() {
        global $db;
    }

    public class Head() {

        public function Description($page) {
            return "SELECT * FROM `$db['database']`.`desciption` WHERE `page` = '$page'";
        }

        public function Keywords($page) {
            return "SELECT * FROM `$db['database']`.`keywords` WHERE `page` = '$page'";
        }
    }
}

$sql = new SQL();
echo $sql->Head()->Description('home'); //For testing

• Is it possible to nest classes in PHP?
• If so, how is it done?

Answer 1

Try it like this

<?php
require( $_SERVER['DOCUMENT_ROOT'] . '/#some_db_directory/database.php');
//This file contains $db['host'], $db['user'], etc...

class SQL {
    public $sql;
    private $_head;

    public function __construct() {
        global $db;
        $_head = new HeadClass();
    }

    public function Head() {
        return $this->_head;
    }
}

class HeadClass { // Class cannot have a public access modifier

    public function Description($page) {
        return "SELECT * FROM `" . $db['database'] . "`.`desciption` WHERE page = $page";
    }

    public function Keywords($page) {
        return "SELECT * FROM `" . $db['database'] . "`.`keywords` WHERE page = $page";
    }
}

$sql = new SQL();
echo $sql->Head()->Description('home.html');
?>

I am moving the class declaration outside the class and creating an instance of the class with in SQL. This is then made available via the Head() function.

Note: For body you will need to create a separate class and use a reference in the SQL class to it like I have done for head.