#20065 [NEW]: References to object members seem to be backwards

From: mattb@columbia.edu Operating system: GNU/Linux 2.4.18-17.7.x (RedHat) PHP version: 4.2.3 PHP Bug Type: Class/Object related Bug description: References to object members seem to be backwards I have stumbled onto a reference behavior I cannot explain. Here's my problem: I'm trying to return a copy of a member variable. The function is not declared to return a reference, but it seems as if the user can override this. Here's a non-object example: <?php // Create an array $array = array('foo', 'bar', 'baz'); // This function merely returns a copy of the array function testArray() { global $array; return $array; } // Grab the return from the function (notice the '&') $copiedArray = &testArray(); // Modify it $copiedArray[] = 'quux'; // Print the original and the copy out echo "=== array ===\n"; var_dump($array); echo "=== copiedArray ===\n"; var_dump($copiedArray); ?> Running this yields exactly what you would expect: === array === array(3) { [0]=> string(3) "foo" [1]=> string(3) "bar" [2]=> string(3) "baz" } === copiedArray === array(4) { [0]=> string(3) "foo" [1]=> string(3) "bar" [2]=> string(3) "baz" [3]=> string(4) "quux" } So far, so good. This is as expected (even if the caller tries to use the '&', he's getting the reference to the copy). Now instead of a global array, let's try the exact same thing with a member of a global object: <?php // Dummy class class Test { var $array; } // Instantiate it $object = &new Test(); // Create a member that is an array $object->array = array('baz', 'bar', 'foo'); // Same function as before, only it's returning a // member variable function testObject() { global $object; return $object->array; } // Grab the return from the function (notice the '&') $copiedArray = &testObject(); // Modify it $copiedArray['lyx'] = 'quux'; // Print the original and the copy out echo "=== array ===\n"; var_dump($object->array); echo "=== copiedArray ===\n"; var_dump($copiedArray); ?> Here, I would expect that the results would be exactly the same (remember, there are absolutely no references in the declaration of testObject() or in the body; everything *should* be a copy). Here's what gets printed when this is run: === array === array(4) { [0]=> string(3) "baz" [1]=> string(3) "bar" [2]=> string(3) "foo" ["lyx"]=> string(4) "quux" } === copiedArray === array(4) { [0]=> string(3) "baz" [1]=> string(3) "bar" [2]=> string(3) "foo" ["lyx"]=> string(4) "quux" } Whoa! $copiedArray is now a reference for the member variable! But look what happens if I redefine the function slightly: function testObject() { global $object; $array = &$object->array; return $array; } Now I get what I expect again ($copiedArray doesn't point to the member variable after calling testObject()). So what gives? Why is "return $object->member;" exempt from the return declaration of the function? This is an interesting "feature". Not very intuitive...I'd call it a bug. Has anyone else noticed this? The above behavior happens with scalars (e.g., strings, numbers) too, not just arrays. Now for something REALLY weird. Check this out: <?php // Dummy class class Test { var $myString; } // Instantiate it $object = &new Test(); // Create a member $object->myString = 'hello'; // Test function function testObject() { global $object; // Make a copy of the member variable (no '&') $newString = $object->myString; // Return the COPY return $newString; } // Grab the return from the function (notice the '&') $copiedString = &testObject(); // Modify it $copiedString = 'goodbye'; // Print the original and the copy out echo "=== array ===\n"; echo $object->myString . "\n"; ?> Here's the output: === array === goodbye Huh?! I even made a copy inside the function! Note that just as before (see original message), the following change "fixes" things: function testObject() { global $object; // Create a reference to the member variable $newString = &$object->myString; // Return the reference return $newString; } Now the output is as expected(?): === array === hello So (at least according to these tests) it seems that reference handling of object data members is somewhat inconsistent with the rest of the world (and of the PHP language specification, from what I understand). -- Edit bug report at http://bugs.php.net/?id=20065&edit=1 -- Try a CVS snapshot: http://bugs.php.net/fix.php?id=20065&r=trysnapshot Fixed in CVS: http://bugs.php.net/fix.php?id=20065&r=fixedcvs Fixed in release: http://bugs.php.net/fix.php?id=20065&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=20065&r=needtrace Try newer version: http://bugs.php.net/fix.php?id=20065&r=oldversion Not developer issue: http://bugs.php.net/fix.php?id=20065&r=support Expected behavior: http://bugs.php.net/fix.php?id=20065&r=notwrong Not enough info: http://bugs.php.net/fix.php?id=20065&r=notenoughinfo Submitted twice: http://bugs.php.net/fix.php?id=20065&r=submittedtwice register_globals: http://bugs.php.net/fix.php?id=20065&r=globals PHP 3 support discontinued: http://bugs.php.net/fix.php?id=20065&r=php3 Daylight Savings: http://bugs.php.net/fix.php?id=20065&r=dst IIS Stability: http://bugs.php.net/fix.php?id=20065&r=isapi