Help with Classes

[wsfowler]

I'm trying to call a function from one class within another class and I just can't seem to get it to work. Here's some pseudo code. Note that each class is in a separate file.

// File1.php
class Database {
function Database() {
// Init code here
}
function OpenDatabase() {

// open the database
}

}

$database = new Database();

// File2.php
require("File1.php");

class Categories {
function Categories() {
//Init code here
}
function GetAllCategories() {
global $database;
if ( $database->OpenDatabase() )
//Get the categories in the database

else
// die
}
}

When I try to run this code, I get the error: "Fatal error: Call to a member function on a non-object" and it references the "$database->OpenDatabase()" line.

So apparently the $database variable doesn't contain the class information. Would this have anything to do with 'register_globals' being off? I've been pulling my hair out for hours!

Thanks in advance for any help!

[kellog]

That's a really wierd way of doing that. Try something like this:

<?
//OnlyFile.php

class Categories
{
	//Init code here
	// Open the database

function GetAllCategories()
{
	//Get categories code
}
}
?>

[wsfowler]

I could certainly do it like you suggest, but I'd like to keep my classes as general as possible. Let me create a more generic example:

class A {
function do_something() {
}
}

$a = new A;

class B {
function something_else() {
global $a
$a->do_something();
// something_else
}
}

I've tried coding this up, but it doesn't work. How would I code this so it does work. It boils down to how do you call the function of one class from within a function of another class?

[kellog]

I've done this before, and if I remember right it went something liek this:

class A { 
function do_something() { 
} 
} 

class B { 
function something_else() { 
$a = new A; 
$var = $a->do_something(); 
// something_else 
} 
} 

[kellog]

Confirmed: this worked on my server.

//class file
class a
{
        function test1()
        {
                $var = "hello";       

                return $var;
        }
}

class b
{
        function test2()
        {
                $test = new a;
                $result = $test->test1();
                return $result;    

        }
}

// php script file
include ("test.class");

$tester = new b;
$whatever = $tester->test2();

echo $whatever;

[laserlight]

As per your original intention, you could also use:

class a
{
	function test1()
	{
		return "hello";
	}
}

$a_obj = &new a;

class b
{
	var $a;
	function b(&$a) {
		$this->a = $a;
	}
	function test2()
	{
		return $this->a->test1();
	}
}

$tester = new b($a_obj);
echo $tester->test2();

I think the main problem with Kellog's suggestion is that each object instantiated would then have its own database connection, once you apply the technique to the database abstraction layer.

[ahundiak]

The original code (with a few minor syntax tweaks) you posted works. You probably want to use require_once instead of require so only one database object is created. But look elsewhere to solve whatever problem it is that you have.