What are the differences between using "self.close()" and "top.close()" for closing windows in PHP scripts?

Using "self.close()" will close the current window/tab where the script is running, while "top.close()" will close the topmost window in the window hierarchy, which may not necessarily be the current window. Therefore, if you want to close the current window, you should use "self.close()", but if you want to close the topmost window, you should use "top.close()".

// Close the current window/tab
echo '<script type="text/javascript">self.close();</script>';

// Close the topmost window
echo '<script type="text/javascript">top.close();</script>';