Description:
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Using ArrayIterator::ksort() without any arguments generates ArgumentCountError error.

Issue seems related to implementation of this feature request https://bugs.php.net/bug.php?id=62840.

Test script:
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<?php
$array = [];
$arrIter = new ArrayIterator($array);
$arrIter->ksort();

Expected result:
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As per https://github.com/php/php-src/blob/4fa3687e56050a111e8eaffe330258003628225e/ext/spl/spl_array.stub.php#L191
the new $sort_flags arguments has a default value. (In PHP 7 the method does not have any arguments).

So I do not expect any error to be generated when calling the method without any argument.

Actual result:
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Above example code generate error like:

Fatal error: Uncaught ArgumentCountError: ArrayIterator::ksort() expects exactly 1 parameter, 0 given