PHP 4.0 Bug #8740 Updated: $this can't be passed by reference inside of constructor
| From: | waldschrott@php.net | Date: | Tue, 16 Jan 2001 22:53:15 +0000 |
| Subject: | PHP 4.0 Bug #8740 Updated: $this can't be passed by reference inside of constructor | ||
| Groups: | php.dev | ||
| Request: | Send a blank email to php-dev+get-44285@lists.php.net to get a copy of this message | ||
ID: 8740
Updated by: waldschrott
Reported By: florian.ortner@nme.at
Old-Status: Open
Status: Closed
Bug Type: *General Issues
Assigned To:
Comments:
you did not quite understand:
1) add a &, like below
it should read, on the global scope:
$a = &new a(10);
2) remove that xtra line
$a->x();
and you'll see that it works
this is due to the fact NEW returns a copy be default
Previous Comments:
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[2001-01-16 15:26:12] florian.ortner@nme.at
no, that's the opposite of what i wanna get.
$this->b = new b($this); is instancing and assigning a new object of type b to $this->b BUT
not passing $this by reference to b's constructor.
$foo =& new foobar(); ofcourse doesn't change this behaviour.
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[2001-01-16 13:15:12] waldschrott@php.net
try this:
$foo =& new foobar();
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[2001-01-16 12:55:26] florian.ortner@nme.at
just in case, if i change a's constructor to
function a($i) {
$this->bla = $i;
$this->b = new b(&$this); // note the &
}
it doesn't work either.
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[2001-01-16 12:51:24] florian.ortner@nme.at
the following code-snippet illustrated the problem:
-----
class a
{
var $bla; // some intvalue
var $b; // object of type b
function a($i) {
$this->bla = $i;
// the next line ain't working in the constructor
//$this->b = new b($this);
}
function x() {
// the next line behaves like expected
$this->b = new b($this);
}
function p() {
echo "a::p ".$this->bla."<br>";
}
}
class b
{
var $a; // reference to object of type a
function b(&$a) {
$this->a = &$a;
}
function p() {
echo "b::p ".$this->a->bla."<br>";
}
}
$a = new a(10);
$a->x(); // works
$a->p();
$a->b->p();
$a->bla = 11;
$a->p();
$a->b->p();
-----
output:
a::p 10
b::p 10
a::p 11
b::p 11
-----
this is the wanted behaviour. var $a->b contains a object of type b which contains a reference
back to object $a. object b is instanciated and assigned via the $a->x() methodcall. so far,
nothing special.
when i want to get rid of the additional method in a (that's the x() method) and instanciate b
inside of a's constructor and assign it to $a->b with $this, $a->b->a doesnt contain a
reference to the calling a object but a copy of it.
thus, $this isn't really working inside of an object's constructor.
afaik do other languages have the same limitation of using $this inside of the constructor due to
address-calculation issues.
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Full Bug description available at: http://bugs.php.net/?id=8740