Description:
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When initialize a variable as an integer, and later try to dump a non existent key, PHP dump it as null, and do not drop notice.

If you assign string, it drops the notice.

Test script:
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error_reporting(E_ALL);
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
$array = 666;
var_dump($array);
var_dump($array['test']);
$a = $array['test'];
var_dump($a);

Expected result:
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Notice: Undefined index: test

Actual result:
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null