Description:
------------
Testing $GLOBALS with array_key_exists() gives TRUE as soon as the variable is names anywhere in the code.

This behaviour was not reproduced in PHP7.0.0 or PHP5.

Test script:
---------------
<?php
var_dump(array_key_exists('var', $GLOBALS)); // false
?>

with a var affected after :
<?php
var_dump(array_key_exists('var', $GLOBALS)); // true
$var = 'foo';
?>

with a var simply named in the code:
<?php
var_dump(array_key_exists('var', $GLOBALS)); // true
if (1 == 0) { $var = 'foo'; }
?>

Expected result:
----------------
All tests should give false.