Description:
------------
Why is print? Array ( [a] => baa )

Reproduce code:
---------------
<?php
    $a['a'] = 'aaa';
    $a['a']['a'] = 'bbb';
    
    print_r($a);
?>

Expected result:
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Array ( [a] => Array( [a] => bbb ) )

Actual result:
--------------
Array ( [a] => baa )