Call to a member function query() on a non-object

[peter_anderson]

I am changing my script from connecting to the database within every function, to using one connection (in the main class).

 

However, I am getting an error:

Call to a member function query() on a non-object

 

Here is  the main class:

<?php
class main{
// the configuration vars
public $config;
// the current user variables
public $uid = 0; // contains the user ID
public $gid = 0; // contains the group ID
// database variables
public $DB; // contains the connection
public $query_id; // contains the query ID
public $query_count; // how many queries have there been?
// cache variables
public $cache;
public $test = 'hi';
// initiate
public function __construct(){
}
// start up functions
public function startup(){
	// first, set up the caching
	if($this->config['use_memcache'] == true){
		// start up cache
		require_once('cache.class.php');
		$this->cache = new cache_TS();
	}
	// now, set up the DB
	$this->connectToDatabase();
	// now, set up the user session
	$this->setUserSession();
	// are we logged in? If so, update our location
	if($this->uid > 0){
		// update location
		$this->updateUserSession();
	}
}
// connect to database
public function connectToDatabase(){
	// connect to database
	$this->DB = new mysqli($this->config['host'],$this->config['user'],$this->config['pass'],$this->config['db']);
	// were we able to connect?
	if(!isset($this->DB)){
		// this is an error
		exit('could not connect to the database.');
	}
	// test query
	$q = "SELECT id,title FROM topics WHERE id='1' LIMIT 1;";
	$q = $this->DB->query($q);
	$r = $q->fetch_assoc();
	echo $r['id'] . $r['title'];
	// send back
	return $this->DB;
}
// some removed....

 

The test query works fine.

 

It fails here:

<?php
class forum extends main{
public function viewTopic($tid){
	// Connect To Database
	//$sql = new mysqli(db::$config['host'], db::$config['user'], db::$config['pass'], db::$config['db']);		
	// Get assorted details (topic, forum, etc)
	// Get topic details
	$tid = intval($tid);
	$tq = "SELECT * FROM `topics` WHERE id='$tid' LIMIT 1";
	$tq = $this->DB->query($tq);
	$tr = $tq->fetch_assoc();

 

startup in main has already been called before forum is. The DB connects without failure.

 

Can anyone see what the problem is? How can I get $this->DB->query to work? (The query works fine when it's ran in the main class)

[trq]

I'm not going to comment on the actual issue here as the actual design here is completely floored.

 

forum appears to extend main simply because it needs a database connection. This is not the correct way to use inheritance. Object should only extend another object if they are of the same type. eg; dog extends animal.

 

To gain access to a database connection within a class you need to pass the connection in as a dependency. This can be done in a number of ways, the most common is to pass it in through the construct. eg;

 

$db = new MySql;
$form = new forum($db);