Multiple Checkbox PHP

<?
$fields = $_POST['fields'];
if (is_array($fields)) {
echo "<pre>";
print_r($fields);
echo "</pre>";
foreach ($fields as $key=>$val) {
echo "$key -> $val <br />";
}
$content = '<hr><br>';
$content = $content . count($fields);
for ($i=0;$i<count($fields);$i++) {
$content = $content . "<li>$fields[$i]\n";
}
echo $content;
}
?>

<form action="<? $_SERVER["PHP_SELF"];?>" method="post">
<input type="checkbox" name="fields[]" value="name">Machine Name<br />
<input type="checkbox" name="fields[]" value="domain">Workgroup/Domain<br />
<input type="checkbox" name="fields[]" value="make">Make<br />
<input type="checkbox" name="fields[]" value="model">Model<br />
<input type="checkbox" name="fields[]" value="os">Operating System
<input name="submit" type="submit" value="submit">