Description:
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Accessing minus keys should start from the end of the array much like the behavior 
in Perl or Python 

Test script:
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<?php
echo [1, 2, 3][-1] . PHP_EOL;
echo [3, 2, 1][-2] . PHP_EOL;
echo ['foo', 'bar'][-1] . PHP_EOL;

Expected result:
----------------
3
2
bar