Object's array goes blank

Bobulous

I'm stumped by a small amount of object-oriented code I've been working on.

The main script contains a single object of class Keyword_set.

Keyword_set contains an associative array of Keyword objects.

Keyword contains an associative array of Page objects.

Keyword and Page both have a get_object($string) function that should return the relevant object from the relevant array, or create an entry in the array if one does not already exist for that string. (The code structure for this function is exactly the same in both classes.)

The array in Keyword_set seems to hold up fine, but the array in my Keyword objects seems to go blank everytime the script exits the Keyword_set object. An integer value in my Keyword objects can be recalled no problem, so it's just the array that seems to go blank.

Is there something about object data lifetime in PHP 4 that means I'll always lose my array data in objects that are deeper than one reference away?

mrfritz379

post the code of the get_object() method. Is it possible that the code is not finding the array index populated and thus redefining that index every time the code is called?

Bobulous

No, I don't think so. I've got so many echo lines in the code now that I'm pretty sure it all works. It's just that the array data seems to get lost when execution backs up the stack.

 	function get_keyword_object($keyword) {
 		if (!array_key_exists($keyword, $this->set)) {
 			echo "<p>Keyword $keyword not already found in keyword set - new keyword object created.</p>";
 			$this->set[$keyword] = new Keyword;
 		} else {
 			echo "<p style='color: green;'>Keyword $keyword already in keyword set.</p>";
 		}
 		return $this->set[$keyword];
 	}

As I said, the code is the same as this in both classes. The data is there correctly while execution is in the Keyword object, but once execution goes back up the stack the array data in the deepest object seems to be discarded.

mrfritz379

oh I think I know what it is. if you set the array index in the deeper object, then later retrieve that object with the get_object() method, that object's index is not populated, right?

You need to return by reference, using the & in your function names.

function &get_keyword_object($keyword) {
 		if (!array_key_exists($keyword, $this->set)) {
 			echo "<p>Keyword $keyword not already found in keyword set - new keyword object created.</p>";
 			$this->set[$keyword] = new Keyword;
 		} else {
 			echo "<p style='color: green;'>Keyword $keyword already in keyword set.</p>";
 		}
 		return $this->set[$keyword];
 	}

and when calling the object:

$object =& $key->get_keyword_object($somekey);
$object->set_key($somevalue);

see if that helps at all.

Bobulous

Ah, thank you, mrfritz379.

You put me on the right course. It was related to references, but needed a little more work. The working get_keyword_object function now looks like this:

function &get_keyword_object($keyword) {
    if (!array_key_exists($keyword, $this->set)) {
        echo "<p>Keyword $keyword not already found in keyword set - new keyword object created.</p>";
        $this->set[$keyword] =& new Keyword;
    } else {
        echo "<p style='color: green;'>Keyword $keyword already in keyword set.</p>";
    }
    $key =& $this->set[$keyword];
    return $key;
}

I have to say, I'm not impressed with OOP in PHP 4. It sounds like PHP 5 offers a lot of improvements in this area. But my host doesn't provide PHP 5, so I've got PHP 4 installed on my local machine. I ought to be using Java, really.