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Objects are already references in PHP 5, thuse there is no sense in ...&$this in any way.

I still find it a bug. I need a reference to $this for BC with PHP4 in the following piece of code:

    function &getRootDataSource() {
        $root =& $this;
        while ($root->parent != NULL) {
            $root =& $root->parent;
        }
        return $root;
    }

NOTE: This is about PHP 5. It might have worked in PHP 4 but it does not and will not work in PHP 5.

I'm not an expert in PHP internals but there's a guy(stereofrog) on the SitePoint forum who has a different point of view(http://www.sitepoint.com/forums/showpost.php?p=2146304&postcount=9):

[quote]
it's 'simply ridiculous. They have a code in zend_compile.c that handles "$this=$x" and copy-pasted that code in the function that comples assignment by reference. This should prevent "$this=&$x" (which is wrong), but for some reason it "prevents" "$x=&$this" as well (which is absolutely correct). It's pure c-level bug and has nothing to do with "new object model" and other blah-blah.
[/quote]

It's still bogus, you can call it a BC break if you want, but we're not going to change this back.

And why does the following code work then???

<?php

class Foo {
  function Foo() {
    $this->ref =& $this;
    $this->ref->test();
  }

  function test() {
    echo 'test';
  }
}

$foo = new Foo();

?>

It has everything to do with the new object model.  Take this code:

  $x = &$this;
  $x = 'foo';

For performance reasons we need to catch such references when they happen in order to prevent the object being overwritten inside itself.  It would be a bit less confusing if the error happened on the actual assignment, but in this new object model there $x = &$this; is just as wrong as $this = &$x since the only purpose one could have for making a reference to $this itself is if you wanted to change it directly.  In all valid cases this should be $x = $this.

I suppose an option would be to ignore the reference in this case and continue on.  That seems to be happening with that last indirect case you posted, but it would cost us a lookup.

Fixed in CVS HEAD and PHP_5_1.

So for the curious who are wondering what "fixed" means.  The & is simply ignored in this case now. 

I'm reopening this so that we can discuss it. I don't think we should be silently ignoring references as that's something vague. See mail to internals@ in a bit.

Guys your notes about possible misuse($ref =& $this;$ref = 'foo') are totally valid but is soooooo much difficult to spot this situation _when_it_actually_happens_? 

I'm by no means going to use this ref improperly but simply want BC with PHP4...

This bug is fixed.

Disallowing $a = &$this; and foo(&$this) is a feature request (not a bug). Also I don't see any sense no breake BC and valid code only because this assignment is dangerous.

$this = mysql_last_id();

I got the same error as previously stated. Worked fine in PHP 4. I use the variable $this in the very next line of code for a database entry, but it keeps kicking back fatal errors at this line.

It is not allowed anymore for obvious reasons. Please read the migration guide and the PHP manual for more details.