Description:
------------
I have ported some code from PHP 5 to PHP 7 and founds strange behavior - seems global variables are reserved (?) before execution.
I wrote simple test code: https://3v4l.org/teWDV
Is this expected backward incompatible changes or bug?
This peace of code wants to provide "system" global variables w/o override existed (I know that is so ugly...), what i must do?
For example, rewrite the function:
function provideGlobals() {
	$GLOBALS += array("foo" => "foo");
}

to something like this:
function provideGlobals() {
	foreach(array("foo" => "foo") as $key => $val)
	{
		if(!isset($GLOBALS[$key]))
		{
			$GLOBALS[$key] = $val;
		}
	}
}

Test script:
---------------
<?php

function provideGlobals() {
	printf("Is foo exists: %d\n", array_key_exists("foo", $GLOBALS));
	$GLOBALS += array("foo" => "foo");
}

provideGlobals();
echo $foo;

Expected result:
----------------
Is foo exists: 0
foo

Actual result:
--------------
Is foo exists: 1

Notice: Undefined variable: foo in /in/teWDV on line 9