dirname() retrieves the directory name of a file path. You may also specify the path levels to be retrieved at PHP version 7.0.

<?PHP
	$file="C:\Windows\win.ini";
    echo dirname($file); //C:\Windows
	
	$file="C:\Windows\win.ini";
    echo dirname($file, 2); //C:
?>

It also supports URL file name.

<?PHP
	$file="http://https://convert.idontcarewhatyouthink.net/program/php/dirname.php";
    echo dirname($file);
	//http://https://convert.idontcarewhatyouthink.net/program/php
?>

Following code will determine the file path of current file. Because there is no slash in the path, so a dot (•) is returned.

<?PHP
	echo dirname("_FILE_");  //.
?>