Description:
------------
Trying to concatenate on to a new/empty array element with the array push assignment operator, [] =, causes PHP to create a fatal error.

This is tested with the CVS snapshot http://snaps.php.net/php5-200504260830.tar.gz

Although the code I have given below is technically not correct because you can not concatenate a string on to an empty/new array element, it should be seen as an warning and not a fatal error (See notes on expected result). Also, the error is not very descriptive from a end user's point of view. I assume the invalid opcode error is obviously a generic error message that is used by you guys at Zend for debugging.

Previous versions of PHP seem to inconsistent. The reproducable code doesn't even give me a warning message when tested under PHP5.0.4. Surely it would be right to make this consistent with concatenating an undefined variable, by making a "Notice: Undefined variable: test[]" error.

Reproduce code:
---------------
<?php 
$test = array();
$test[] .= 'blah';
?>

Expected result:
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Some form of warning stating that you can not concatenate to an empty/undefined array element. This should be consistent with the fact that if you did...

<?php
$f .= 'foo bar';
?>

that you would get a warning message because $f has not been defined before. (i.e. Notice: Undefined variable: f)

Actual result:
--------------
Fatal error: Invalid opcode 30/16/8