Get the physical (MAC) address of the machine's network card

/**
 Get the physical (MAC) address of the machine’s network card
**/
class GetMacAddr
{
 var $return_array = array(); // Return a string array with MAC address
 var $mac_addr;

 function GetMacAddr($os_type)
 {
 switch ( strtolower($os_type) )
 {
 case "linux ":
 $this-> forLinux();
 break;
 case "solaris ":
 break;
 case "unix ":
 break;
 case "aix ":
 break;
 default:
 $this-> forWindows();
 break;
 }

 $temp_array = array();
 foreach ( $this-> return_array as $value )
 {
 if ( preg_match( "/[0-9a-f][0-9a-f][:-] ". "[0-9a-f][0-9a-f][: -] ". "[0-9a-f][0-9a-f][:-] ". "[0-9a-f][0-9a-f][:-] ". "[0- 9a-f][0-9a-f][:-] ". "[0-9a-f][0-9a-f]/i ", $value, $temp_array ) )
 {
 $this-> ; mac_addr = $temp_array[0];
 break;
 }
 }
 unset($temp_array);
 return $this-> mac_addr;
 }

 function forWindows()
 {
 @exec( "ipconfig /all ", $this-> return_array);
 if ( $this-> return_array )
 return $this-> return_array;
 else{
 $ipconfig = $_SERVER[ "WINDIR "]. "system32ipconfig.exe ";
 if ( is_file($ipconfig) )
 @exec($ipconfig. " /all ", $this-> return_array);
 else
 @exec($_SERVER[ "WINDIR "]. "systemipconfig.exe /all " , $this-> return_array);
 return $this-> return_array;
 }
 }

 function forLinux()
 {
 @exec( "ifconfig -a ", $this-> return_array);
 return $this-> return_array;
 }
}
?>
$mac = new GetMacAddr(PHP_OS);
echo $mac-> mac_addr;
?>