[SOLVED] calling an objects method within another object

[andy_b42]

I am fairly new to using objects in php. I have made a fairly simple database object so i can just call one of a few of my own methods to automatically make changes to the database when i change the relevant object. Below is a very simplified version of what i am trying to accomplish:

 

Class Database{

  public function Query($query){

      //connect to database, run query and return result

  }

}

 

Class User{

  private $username;

  private $db;

 

  public function __construct($intID){

      $this->db = new Database();

      if($intID > 0){

        getUserData($intID);

      }

  }

 

  public function getUserData($intID){

      $sql = "select * from users where intID = $intID";

      return $this->db->Query($sql);

  }

}

 

The problem i get is when "$this->db->Query($sql);" is executed and the error i get is:

"Fatal error: Call to a member function Query() on a non-object"

 

According to the IDE i am using, the function is accessible, but it seems when running the code, the parser cannot see that $this->db is an object with functions.

 

My question is, is what i am attempting to do possible or am I missing something very basic to make this work?

 

Thanks

[trq]

My question is, is what i am attempting to do possible or am I missing something very basic to make this work?

 

Not only is it possible, but the example you have supplied should actually work. Although this....

 

public function __construct($intID){
      $this->db = new Database();
      if($intID > 0){
         getUserData($intID);
      }
   }

 

should be....

 

public function __construct($intID) {
  $this->db = new Database();
  if ($intID > 0) {
    $this->getUserData($intID);
  }
}

[RichardRotterdam]

It should work indeed can't find an error. Unless you do something like this to call the function

 

User::getUserData(0);

instead of

$user=new User();
$user->getUserData(0);

 

what does the code look like to instantiate the user?

[andy_b42]

Thanks for the quick replies

 

The objects i am actually using are a lot more complex than what i have posted here: below are the database and user objects

 

http://andyb42.servebeer.com:4567/phpfreaks/database.txt

http://andyb42.servebeer.com:4567/phpfreaks/user.txt

 

The user is instantiated like this "$user = new User($intID);", the constructor then does all of the work filling in the users data from the database.

[trq]

So what error do you recieve with these objects?

[andy_b42]

Fatal error: Call to a member function Query() on a non-object

[trq]

The only thing I can think of that might be happening is that your Database class isn't being included properly. I would use require_once instead of include. You might also turn display errors on and set error reporting to E_ALL.

[RichardRotterdam]

Look in your User class

in the function load you have this

$user = mysql_fetch_array($db->getResult());

 

change $db to $this->db

 

also use __construct() instead of User() it fits tidier into php5 syntax

[andy_b42]

Look in your User class

in the function load you have this

$user = mysql_fetch_array($db->getResult());

change $db to $this->db

 

Thanks, that line was like that becuase the only way i can make this work was to create the $db object outside the calss and then inside the function, use global $db and the call it as though $db were a variable local to that method.

[RichardRotterdam]

Using a global db would be better since you wouldnt have to instantie the db object multiple times.

 

you could do this in your constructor

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

[andy_b42]

i was under the impression that global variables are not very secure.

 

Also, is there a chance that if i use 2 or more objects on the same page, the $db variables (for simplicity sake i would like to call it the same thing in every object) would get mixed up?

 

It is quite important that each instance of the $db variable is unique to the object becasue the Database class holds the results of the query which are then used by the object if they are required.

[andy_b42]

my sincere apologies for wasting everyones time... I fell like a complete idiot, in the User constructor i had called the load() before creating the $db object

 

Original:

public function User($intID = 0){
		if($intID > 0){
			$this->load($intID);
		}else{
			//echo "No " . $this->currentClass . "ID information supplied";
		}

		try{
			$this->db = new Database();
		}
		catch(Exception $exc){
			echo "Error creating database object";
		}
	}

 

Should be:

public function User($intID = 0){
		try{
			$this->db = new Database();
		}
		catch(Exception $exc){
			echo "Error creating database object";
		}

		if($intID > 0){
			$this->load($intID);
		}else{
			//echo "No " . $this->currentClass . "ID information supplied";
		}
	}