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Doc Bug #73981 __construct not being called on extensions of DOM base classes
Submitted: 2017-01-23 18:13 UTC Modified: 2021-07-09 12:45 UTC
Avg. Score:3.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:0 (0.0%)
Same OS:0 (0.0%)
From: work at timothytown dot com Assigned:
Status: Verified Package: DOM XML related
PHP Version: 7.1.1 OS: windows
Private report: No CVE-ID: None
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From: work at timothytown dot com
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 [2017-01-23 18:13 UTC] work at timothytown dot com
When a class is registered to a DOMDocument via the registerNodeClass method, the assigned class is used to instance the return object from the DOMDOcument. However, the construct method of that class is not called. 

Test script:
class SillyTestClass extends DOMElement{
    public $foo=null;
    public function __construct($name,$value=null,$namespace=null){
        echo "calling child construct....";
    public function sayHello(){
        echo "Why, hello there!";

$doc=new DOMDocument();

//THIS IS STILL NULL:( Never set by construct, no message saying construct was called either  
echo $doc->documentElement->firstChild->foo; 

Expected result:
output "calling child construct..." //printed from child _construct
output "Why, hello there!" //printed from child method sayHello()
output "bar" //the value of child property after being assigned in constructor

Actual result:
//only the sayHello() method fires; construct doesn't happen
Why, hello there;


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 [2017-01-24 11:30 UTC]
-Package: *General Issues +Package: DOM XML related
 [2018-07-27 12:24 UTC]
-Status: Open +Status: Verified
 [2018-07-27 12:24 UTC]
Confirmed: <>.
 [2021-07-09 12:45 UTC]
-Type: Bug +Type: Documentation Problem
 [2021-07-09 12:45 UTC]
The problem is: which arguments should be passed to the
constructor of the custom class?  This can't be determined,
because constructors are exempt from signature checks on
inheritance, so arbitrary parameters could be expected.  Even if
it we would enforce that the signature of the custom class would
match the one of the parent (what could be confusing and
restricting), it may not be possible to implement that.

Given that ::registerNodeClass() has the already documented
limitation that re-created instances loose their property values,
I think it's best to document the quirk that the constructors are
not called as well, and to leave it at this.
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Last updated: Mon Mar 27 11:03:36 2023 UTC