<?php
echo defined('__DIR__') ? '__DIR__ is defined.' : '__DIR__ is NOT defined.';
echo "\n\n";

echo @__DIR__;
echo "\n\n";

echo strlen(__DIR__);
echo "\n\n";

/**
 * Results when testing with PHP 7.0.2 for Windows 7 (executed as "X:/test.php"):
 * __DIR__ is NOT defined.
 *
 * X:\
 *
 * 3
 */