<?php

// Define the parameters for the shell command
$location = "\\servername\sharename";
$user = "USERNAME";
$pass = "PASSWORD";
$letter = "Z";

// Map the drive
system("net use ".$letter.": \"".$location."\" ".$pass." /user:".$user." /persistent:no>nul 2>&1");

// Open the directory
$dir = opendir($letter.":/an/example/path")

...

?>