calling method from another class

irish12

I am just learning object oriented programming, I've been using PHP for a few years though.
I have a little problem.
I have two classes: dbconnection, html_class. html_class extends the dbconnection.
I am calling a dbconnection:Query method from the html_class but I am receiving an error.

$query = $this->Query($sql);

Warning: mysql_query(): supplied argument is not a valid MySQL-Link resource in /home/.cato/dapperco/website.com/includes/class_database_v3.php(81) : eval()'d code on line 1

jonno946

i normally pass my database object by refrence into another.

for example

// make database object
$db = &new MySQL('localhost', 'user', 'pass', 'database');

// make content management object
$cm = new ContentManagement();

// register database object in content management object
$cm->db = &$db;

then call the methods of your database object like this:

$myquery = $this->db->query('SELEC...

Jonno

edit: didnt read ur question properly, have you tried calling parent::query(...?

irish12

jonno946,
I just tried parent::query but I am still getting the same error.
In your sample code, would the MySQL() just return the connection and then $cm->db would assign the connection to a variable? I don't quite understand how it works.
Could you possibly send me a sample of your classes? I really need to get my head around this.

jonno946

In your sample code, would the MySQL() just return the connection and then $cm->db would assign the connection to a variable? I don't quite understand how it works.

yep.

i used to always make my base class include my mysql connections, and then the actual class extend that.

i figured this was a bad idea, as what if other classes which may also include database connection methods) wanted to use the same instance of the database object?

problems... and very messy code...

so instead, i figured the best way was to put all of the database connection stuff in its own class, and then pass an instance of that object to other objects that need database conectivity like this:

$my_object->database_variable = &$database_object;

that way, any changes that are made to the database_variable in object $my_object will be reflected on the main database variable as well.

can you show us the code thats causing the proplem?

Jonno

irish12

ohh, I see. So the database instance is a reference to the class and then pass the reference into the subclass. Then in the subclass assign it to a variable. I'll try that...

Yes, it works, thank you, thank you, thank you.

For anyone that is following this, here is what I did:

Here is the instance of the classes

$db = &new Database('mysql',$dbserver,$dbusername,$dbpassword,$dbdatabase);
$html = new htmlclass(&$db);

and here is the begining of the subclass:

class htmlclass{

var $dbConn = null; 

   function htmlclass($dbConn) 
   { 
      $this->dbConn = $dbConn;
   }

this is the method that is in the subclass which is calling the database class:

function nav_teasers($query){

	while($row = $this->dbConn ->FetchAssoc($query)){
		Echo "<i><div  class='row1'>";
		Print $row["City"];
		print "</div></i>";
		//$this -> teasers($row["CityID"]);
		Print "<p>";
	}
}

jonno946

well done, glad u got it sorted🙂