废话不多讲，直接上代码吧！

复制代码 代码如下:
<?php  
class MacAddr
{  
    public $returnArray = array();   
    public $macAddr;  

    function __contruct($os_type=null){
        if(is_null($os_type)) $os_type = PHP_OS;  
        switch (strtolower($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->returnArray 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->macAddr = $temp_array[0];  
                break;  
            }  
        }  
        unset($temp_array);  
        return $this->macAddr;  
    }

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

    function forLinux(){  
        @exec("ifconfig -a", $this->returnArray);  
        return $this->returnArray;  
    }  
}  

$mac = new MacAddr(PHP_OS);  
echo $mac->macAddr;  
echo "<br />";

// 获取客户端
// linux
$command = "arp -a {$_SERVER['REMOTE_ADDR']}";
echo $command;
echo "<br />";
$result=`{$command}`; 

// windows
$command = "nbtstat -a {$_SERVER['REMOTE_ADDR']}";
echo $command;
echo "<br />";
$result=`{$command}`; 
print_r($result);  
?>

获取服务端的逻辑没什么大问题，可能会存在权限问题。
获取客户端的时候，可能会比较慢，arp/nbstat命令执行会比较慢。

复制代码 代码如下:
<script language="JScript" event="OnCompleted(hResult,pErrorObject, pAsyncContext)" for="foo">   
document.forms[0].lbMacAddr.value=unescape(MACAddr);   
</script>  
<script language="JScript" event="OnObjectReady(objObject,objAsyncContext)" for="foo">   
if(objObject.IPEnabled != null && objObject.IPEnabled != "undefined" && objObject.IPEnabled == true && objObject.MACAddress != null && objObject.MACAddress != "undefined") MACAddr = objObject.MACAddress;   
</script>  
<object id="locator" classid="CLSID:76A64158-CB41-11D1-8B02-00600806D9B6"></object>  
<object id="foo" classid="CLSID:75718C9A-F029-11d1-A1AC-00C04FB6C223"></object>  
<script language="JScript">   
var service = locator.ConnectServer();   
var MACAddr ;   
var IPAddr ;   
var DomainAddr;   
var sDNSName;   
service.Security_.ImpersonationLevel=3;   
service.InstancesOfAsync(foo, 'Win32_NetworkAdapterConfiguration');   
</script>  
<form><input type="text" id='lbMacAddr' name='lbMacAddr' /></form>

只适用于IE浏览器，而且会有告警提示，挺遗憾的。