子目录“。”和“..”| PHP

Question

Why does PHP output two subdirectories that has: . and .. when reading a directory.

From PHP.net:

<?php
$dir = "/etc/php5/";

// Open a known directory, and proceed to read its contents
if (is_dir($dir)) {
    if ($dh = opendir($dir)) {
        while (($file = readdir($dh)) !== false) {
            echo "filename: $file : filetype: " . filetype($dir . $file) . "
";
        }
        closedir($dh);
    }
}
?>

Outputs:

filename: . : filetype: dir
filename: .. : filetype: dir
filename: apache : filetype: dir
filename: cgi : filetype: dir
filename: cli : filetype: dir

Why does it do that?

Answer 1

Because "." and ".." are actual directories (in the *nix world).

"." refers to the current directory
".." refers to the parent directory.

If you do an "ls" you'll see the same exact output.