PHP dirname() function and

Here is the code:

without trailing slash

echo __FILE__ ; // 取得当前文件的绝对地址，结果：D:\www\test.php 
echo "<br>";
echo dirname(__FILE__); // 取得当前文件所在的绝对目录，结果：D:\www\ 
echo "<br>";
echo dirname(dirname(__FILE__)); //取得当前文件的上一层目录名，结果：D:\ 
echo "<br>";

There is a slash at the end

echo __FILE__ . DIRECTORY_SEPARATOR; // 取得当前文件的绝对地址，结果：D:\www\test.php 
echo "<br>";
echo dirname(__FILE__) . DIRECTORY_SEPARATOR; // 取得当前文件所在的绝对目录，结果：D:\www\ 
echo "<br>";
echo dirname(dirname(__FILE__)) . DIRECTORY_SEPARATOR; //取得当前文件的上一层目录名，结果：D:\ 
echo "<br>";