怎么利用PHP去ping一个地址

if(($server == 127.0.0.1) | | ($server == localhost) | | ($server == getenv("SERVER_ADDR"))) {
echo "

---

";
echo "Fuck Off!
";
echo "

---

";
exit;
} else {
if($server =="") {
echo "

请输入url或ip地址:

";
exit;
}
$ip = getenv("REMOTE_ADDR");
$hname = getenv("HTTP_HOST");
echo "Your IP is: $ip
"
."Trying to ping: $server
"
."Using server: $hname";
echo "

---

";
echo "STATS:
";
$command = "ping -c4 $server";
exec($command, $result, $rval);
if(count($result) echo "没有响应
";
echo "

---

";
exit;
}
for ($i = 0; $i echo "$result[$i]
";
}
echo "

---

";#include("powered.txt");}?>