[PHP] Re: extended class question

[Greg Beaver]

Hello again Ed,
This is a tricky thing.  When you define a variable as being private, it 
literally becomes unavailable to child classes, and exists only as the 
var1 variable in objects of class test.  To prove this, try:

<?php
class a {
    private $a;
    function geta()
    {
        return $this->a;
    }
    function seta($a)
    {
        $this->a = $a;
    }
}
class b extends a {
    private $a;
    function echoa()
    {
        echo 'this ' . $this->geta() . "\n";
        echo 'parent ' . parent::geta() . "\n";
    }
    function seta($a)
    {
        $this->a = $a;
        parent::seta($a - 1);
    }
    function geta()
    {
        return $this->a;
    }
}
$b = new b;
$b->seta(2);
$b->echoa();
?>
you can replace the "private $a" in class b with "protected $a" or 
"public $a" with no errors whatsoever, in essence the private variable 
$a has no name outside of the a class - that's what makes it private.

It's a nice feature.  Now we no longer need to document private 
variables.  Users of our classes can simply ignore them and even name 
their own variables exactly the same way with impunity.

Greg
Ed Lazor wrote:
How come the output to this script is "World Trade Center" instead of "Pizza
Delivery"?
Thanks,
Ed
----------------------------------------------------------------
<?php
class test {
        private $var1;
        
        function __construct() {
                $this->var1 = "World Trade Center";
        }
        
        function get_var1() {
                return $this->var1;
        }
        
        function set_var1($data) {
                $this->var1 = $data;
        }
}
class testing extends test {
        function __construct() {
                parent::__construct();
                $this->var1 = "Pizza Delivery";
        }
}
$test2 = new testing();
print "var1 = " . $test2->get_var1() . "<br>";
?>
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