IP:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Ping</title>
</head>
<body>
    <form action="." method="GET">
        IP: <input type="text" name="ip"> <input type="submit" value="Ping">
    </form>
    <pre><?php
        $blacklist 
= [
            
'flag''cat''nc''sh''cp''touch''mv''rm''ps''top''sleep''sed',
            
'apt''yum''curl''wget''perl''python''zip''tar''php''ruby''kill',
            
'passwd''shadow''root',
            
'z',
            
'dir''dd''df''du''free''tempfile''touch''tee''sha''x64''g',
            
'xargs''PATH',
            
'$0''proc',
            
'/''&''|''>''<'';''"''\'''\\'"\n"
        
];

        
set_time_limit(2);

        function 
ping($ip) {
            global 
$blacklist;

            if(
strlen($ip) > 15) {
                return 
'IP toooooo longgggggggggg';
            } else {
                foreach(
$blacklist as $keyword) {
                    if(
strstr($ip$keyword)) {
                        return 
"{$keyword} not allowed";
                    }
                }
                
$ret = [];
                
exec("ping -c 1 \"{$ip}\" 2>&1"$ret);
                return 
implode("\n"array_slice($ret010));
            }
        }

        if(!empty(
$_GET['ip']))
            echo 
htmlentities(ping($_GET['ip']));
        else
            
highlight_file(__FILE__);
    
?></pre>
</body>
</html>