PHP Variable from extended class

Question

I'm trying to retrieve a variable from an extended class. This is how my main class looks:

class SS {
    public $NONE = NULL;
    public $NUMBERS = array("1", "2", "3", "4", "5", "6", "7", "8", "9", "0");
    public $OPERATORS = array("=", "&&", ">", "<", "+", "-", "/", "*", "^");
    public $DBLQUOTES = '"$1"';
    public $SNGQUOTES = "'$1'";
    public $CODE;

    function SuperSyn($sCode, $cLang) {         
        $hLang = new VB6;
        $VB6 = $hLang->__construct();
        echo $VB6->ssAuthor;
    }
}

And my extended class looks like this (I've removed many of the keywords).

class VB6 extends SS {
    public function __construct() {
        $ssAuthor = "James Brooks";
        $ssCSS = "languages/vb6.css";
        $ssNumbers = $NUMBERS;
        $ssKeywords = array("Abs", "Access", "AddItem");
        $ssReserved = $NONE;
        $ssComments = "('.+)";
        $ssOperators = $OPERATORS;
        $ssDoubleQuote = $NONE;
        $ssSingleQuote = $NONE;
    }
}

If I remove the public function __construct being called, PHP bitches that it's expecting a function.

My question is, how can I retrieve a variable from the extended class into my main class?

Tom Haigh · Accepted Answer · 2009-09-01 10:17:35Z

1

The constructor will be called for you when you create an object, so this should work:

function SuperSyn($sCode, $cLang) {                     
     $hLang = new VB6(); //I think you need some parameters here
     echo $VhLang->ssAuthor;
}

However in your VB6 constructor you are currently only assigning local variables, so you wouldn't be able to access ssAuthor externally. Instead you probably want to do something like:

class VB6 extends SS {
    public $ssAuthor;

    public function __construct() {
        $this->ssAuthor = "James Brooks";
        //etc.
    }
}

edited Sep 1, 2009 at 10:17

answered Sep 1, 2009 at 10:12

Tom Haigh

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1 Comment

James Brooks Over a year ago

That's brilliant! Thank you Tom!

KB22 · Accepted Answer · 2009-09-01 10:09:18Z

1

Use php's parent keyword.

PHP parent

answered Sep 1, 2009 at 10:09

KB22

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2 Comments

James Brooks Over a year ago

Where though? Where am I putting the keyword?

KB22 Over a year ago

Check: stackoverflow.com/questions/393204/… There the topic is discussed in detail.

knittl · Accepted Answer · 2009-09-01 10:13:01Z

0

use parent:: or $this-> (depends, i.e. you have two variables with the same name)

answered Sep 1, 2009 at 10:13

knittl

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2 Comments

James Brooks Over a year ago

But where? If I've still got the function in the extended class, where?

knittl Over a year ago

wait. after reading your code again it doesn’t make sense at all. you hold an derived object in the base class? (SS:SuperSyn that is) and why do you re-apply all your member variables? nevertheless, this should work: $ssNumbers = $this->NUMBERS

Jörg · Accepted Answer · 2009-09-01 10:18:07Z

0

I think that there's a logical problem with your expectiation. Why should a function of the class SS know about a variable that only exists in the VB6 subclass?

That would not be a clean inheritance behaviour and reveals a problem with your classes.

Two choices to solve that:

Put the variable in the main class to use it in a function in that class
Put the function using the subclass's variable inside the subclass

(After reading the comments about the parent keyword and ´$this´ variable: I understood the question differently and don't think either of those to would help since the opposite direction is required: parent class function > subclass variable, not subclass function > parent class variable)

edited Sep 1, 2009 at 10:18

answered Sep 1, 2009 at 10:11

Jörg

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2 Comments

James Brooks Over a year ago

Well the idea of this is that you'll be able to create your own classes for different languages, I need to be able to get each of the different syntax rules from the class.

Jörg Over a year ago

If you'll have to fetch individual information from the subclasses it might be a good idea to make the SS class abstract and add an abstract function like ´getSyntaxRules()´ that each subclass has to implement and that returns the rules for that language.

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