Calling db class within another class

Question

I have been playing around with some php classes just trying to learn really but this one has me scratching my head and after lots of searching on SO and google I can't seem to find anything that covers this problem (maybe I'm not wording the search correctly). The config class before used its own pdo connection so I am looking to make sure its not opening a new connection each time, there is another class not shown here but done in the same way and this seems to work. Here is the error:

Call to a member function query() on a non-object in config.class.php on line 15

The only difference I can see that might be causing this is the config class is running a query within the construct where as my other class does not, is this a problem and if so why?

Have tried a few different things but to be honest I just don't understand.. have only been learning php from online resources. Any reading material on this would be appreciated too.

Have been using this db class: https://github.com/indieteq/PHP-MySQL-PDO-Database-Class

class Config
{
    public $db;
    private $config;

    public function __construct()
    {
        global $db;
        $this->db = $db;

        $this->config = array();

        $rows = $this->db->query("SELECT * FROM config");

        foreach($rows as $row) {
            $this->config[$row['setting']] = $row['value'];
        }
    }

    public function __get($setting)
    {
        return $this->config[$setting];
    }

    public function __set($setting, $value)
    {
        $update   =  $this->db->query("UPDATE config SET value = :value WHERE setting = :setting", array("value"=>$value,"setting"=>$setting));

        if($update > 0) {
            $this->config[$setting] = $value;

            return true;
        } else {
            return false;
        }
    }
}

The classes are all called on one file:

require(INCLUDE_PATH . "Db.class.php");

include(INCLUDE_PATH . "languages\\en.php");
include(INCLUDE_PATH . "config.class.php");

$db = new Db();
$config = new Config();

Do not use global $db, as it may be causing you a scoping problem. Instead, pass the $db variable into the Config::__construct(). Add a parameter to the constructor and use $config = new Config($db); (that is called "dependency injection") Before that though, do var_dump($db); after calling new Db() to ensure that object was created. — Michael Berkowski
– Michael Berkowski, Commented Jul 5, 2015 at 12:43
@MichaelBerkowski Thanks for this works perfect!, I have given you an up-vote :) — Izion
– Izion, Commented Jul 5, 2015 at 14:27

Daniel · Accepted Answer · 2015-07-05 12:46:12Z

2

Try this:

$this->db = new Db();

Or give db in paramter

public function __construct($db) ...

and then:

$config = new Config($db);

edited Jul 5, 2015 at 12:46

answered Jul 5, 2015 at 12:43

Daniel

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3 Comments

Michael Berkowski Over a year ago

I think the current method is being done deliberately to avoid creating multiple connections, as this will do every time new Db() is called

Izion Over a year ago

@Daniel Thanks for the help it all seems to work as planned now. Michael got there just before you but wondering too accept the answer to help others as you edit is correct?

iBrazilian2 Over a year ago

@MichaelBerkowski, It's the only answer available anyway haha

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