Cs computer science

Need explanation ..

“. dirname($parent_dir) .”

“;
$str_result .= “

“;
if ($handle = opendir($parent_dir))
{
while (false !== ($file = readdir($handle)))
{
if(in_array($file, array(‘.’, ‘..’))) continue;
if( is_dir($parent_dir . “/” . $file) ){
$str_result .= “
• ” . read_dir_content($parent_dir . “/” . $file, $depth++) . “

“;
}
$str_result .= “

• {$file}

“;
}
closedir($handle);
}
$str_result .= “

“;

return $str_result;
}
//echo dirname(__FILE__);
echo “

“.read_dir_content(dirname(__FILE__)).”

“;
?>