You can view demo and download how get system Mac Address using PHP:
// Turn on output buffering
ob_start();
//Get the ipconfig details using system commond
system('ipconfig /all');
// Capture the output into a variable
$mycom=ob_get_contents();
// Clean (erase) the output buffer
ob_clean();
$findme = "Physical";
//Search the "Physical" | Find the position of Physical text
$pmac = strpos($mycom, $findme);
// Get Physical Address
$mac=substr($mycom,($pmac+36),17);
//Display Mac Address
echo $mac;
//If you want you can track the page visitor's mac address and store in database
//Insert the visitor's mac address to database
// " INSERT INTO `table_name` (`column_name`) VALUES('".$mac_address."') ";
This is a simple and effective way of getting the client system Mac address using PHP. Hope it will help you.