Description:
------------
Unqualified function calls are supposed to resolve to functions within their namespace if they exist. This doesn't always happen if the in-namespace function doesn't exist when the calling function is defined.

Seen issue on 5.6.28, 5.6.30, 7.1.2

More verbose example: https://paste.laravel.io/9qgML

Test script:
---------------
<?php
namespace NotGlobalNamespace;
eval('namespace F\\o\\o; function bar($marker) { echo "$marker => " . rand() . "\n"; }');
\F\o\o\bar(1);
eval('function bar($m) { return \F\o\o\bar($m); }');
bar(2);
eval('namespace F\\o\\o; function rand() { return "*** INTERCEPTED ***"; }');
\F\o\o\bar(3);
bar(4);
eval('namespace F\\o\\o; function baz($marker) { echo "$marker => " . rand() . "\n"; }');
\F\o\o\baz(5);
eval('function baz($m) { return \F\o\o\baz($m); }');
baz(6);
bar(7);

Expected result:
----------------
1 => 1059777682 (random)
2 => 1332050858 (random)
3 => *** INTERCEPTED ***
4 => *** INTERCEPTED ***
5 => *** INTERCEPTED ***
6 => *** INTERCEPTED ***
7 => *** INTERCEPTED ***


Actual result:
--------------
1 => 1059777682 (random)
2 => 1332050858 (random)
3 => 1123318855 (random)
4 => 1146230506 (random)
5 => *** INTERCEPTED ***
6 => *** INTERCEPTED ***
7 => 360960634 (random)