Re: Variable Scope from child to parent
| From: | Andrew Ballard | Date: | Thu, 15 May 2008 12:50:19 +0000 |
| Subject: | Re: Variable Scope from child to parent | ||
| References: | 1 2 | Groups: | php.general |
| Request: | Send a blank email to php-general+get-274367@lists.php.net to get a copy of this message | ||
Ok, I forgot to reply-all to the list. Here we go again.
On Wed, May 14, 2008 at 6:33 PM, Tyson Vanover <tvanover@pdx.edu> wrote:
> I am trying to get a child class to pass an array of valid keys to it's
> parent when the constructor is run, and the parent appends the data to one
>> of it's array of valid keys. Then it walks through an array pulling out
> values that have valid keys, and putting them in an array for processing
> later. I have tried explicitly stating the variable scope.
>
> abstract class parentclass
> {
> protected $vkeys= array('title1','title2','title3');
> protected $a;
>
> function __construct($set = NULL, $special = NULL)
> {
> self::$this->vkeys= array_merge(self::$this->vkeys, $special);
> foreach($set as $key=>$value)
> {
> if (in_array($key,self::$this->vkeys))
> {
> $this->a[$key] = $value;
> }
> }
> print_r(self::$this->vkeys); //output below
> print_r(self::$this->a); //output below
> }
> }
>
> class childclass extends parentclass
> {
> protected $vkeys= array('titleA', 'titleB', 'TitleC');
>
> function __construct($set, $special = NULL)
> {
> parent::__construct($set, self::$this->vkeys);
> unset(self::$this->vkeys);
> }
> }
>
> Unfortunately it seems to duplicate the child's array instead of appending.
> Explicitly stating scope does not seem to help.
>
>
> print_r(self::$this->vkeys);
> Array (
> [0] => titleA
> [1] => titleB
> [2] => titleB
> [3] => titleA
> [4] => titleB
> [5] => titleB
> )
>
> print_r(self::$this->a);
> Array()
>
> Any thoughts?
A couple. First, as Gabriel said, replace self::$this-> with just
$this->. Second, the protected variable $vkeys in the childclass
effectively overwrites the variable of the same name in the parent
class, so it already has the values you are trying to merge
(array('titleA', 'titleB', 'TitleC')) when the childclass is
instantiated before you even call the constructor. That's why the
constructor duplicates the values. Try this for the constructor for
your childclass:
function __construct($set, $special = array())
{
$merged = array_merge($special, array('titleA', 'titleB',
'TitleC'));
parent::__construct($set, $merged);
}
Andrew
>