make ping with PHP

I would like to make a simple monitoring. I make this:

Code:

<?php
$ip = $_SERVER['127.0.0.1'];
exec("ping -n 4 $ip 2>&1", $output, $retval);
if ($retval != 0) { 
echo "no!"; 
} 
else 
{ 
echo "yes!"; }
?>

I use my internal IP: 127.0.0.1.
The result is: NO!

why???

 

I change this code and I put this:

Code:

IP: 10.110.206.123 (
<?php
$ping_ex = exec("ping -n 1 10.140.206.123", $ping_result, $pr);
if (count($ping_result) > 1){
echo "<img src=\"on.png\">";
} else{
echo "<img src=\"off.png\">";
}
?> )


IP: 127.0.0.1 (
<?php
$ping_ex = exec("ping -n 1 127.0.0.1", $ping_result, $pr);
if (count($ping_result) > 1){
echo "<img src=\"on.png\">";
} else{
echo "<img src=\"off.png\">";
}
?> )

In the first case the resulst are NO and the second case are YES.
But... the result is YES in two cases. Why???

 

yeah!
finally I put this code:

Code:

<?php
$str = exec("ping -n 1 -w 1 100.100.100.100", $input, $result);
if ($result == 0){
echo "<img src=\"on.png\">";
}else{
echo "<img src=\"off.png\">";
}
?>

It's run correctly, but i would like to insert this code into a javascript function because I insert many times this PHP and the page is very hard to load.
I would like to insert a button:

Code:

<input type="submit" onClick="para();">

and when I press this button, the javascript runs.
Is it possible??

 

So, can this code be used for performing DOS attacks on sites??

 

What is theuse of this code?
And how to run this script?