Description:
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You have paradox in error reporting "unset" function
I thing, that logic mast be simple as in "isset" function
I'm confuze by notice from this simple example.
I'm always use maximum error_reporting and analyze logs and this is actual problem.

Reproduce code:
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<?
error_reporting(E_ALL);
ini_set('display_errors', 1);
$nonexisten = array();
unset($nonexisten); // no error
unset($nonexisten); // no error
unset($nonexisten[0]); // notice
$nonexisten = array(0);
unset($nonexisten[0]['name']); // no error
?>

Expected result:
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<b>Notice</b>:  Undefined variable: nonexisten in <b>PHPDocument2</b> on line <b>7</b><br />