When opcache.use_cwd=0 include/require of relative paths from different directories will both resolve to the same (first) file.
Example dir structure:
app1
index.php
lib.php
app2
index.php
lib.php
both index.php(s):
include "lib.php";
app1/lib.php:
echo "app1";
app2/lib.php:
echo "app2";
both will echo "app1".