表单提交时使用BlockUI.js

Question

I write PHP to exec some system command in my Ubutu server. It should be waiting a period and and this time I want show loader waiting. Now, I exec directly, and not use ajax. How can I show show loader during form submit and hide loader when it dones?

Here is my php code:

 <?php
 if(isset($_POST['check_ip']))
 {
     $ip = "localhost";
     $user = 'root';
     $pass = 'letmein';
     $connection =  ssh2_connect($ip, 22);
     ssh2_auth_password($connection,$user,$pass);
     $stream = ssh2_exec($connection, 'ifconfig');
     stream_set_blocking($stream, true);    
     print "<pre>".stream_get_contents($stream)."</pre>";
     exit;
 }
?>

And form HTML:

 <div class="col-md-3">
   <div class="form-group">
      <label style='font-size:15px;color:black'>SHOW IP</label>
      <button name="check_ip" type="submit" id="check_ip" class="btn btn-primary btn-fill pull-center" onclick="return confirm('RELLY?')"><b>SHOW IP<b></button>    
   </div>
</div>