<?php

$all = file_get_contents('./textfile.txt', true);
$success = file_get_contents('./textfile2.txt', true);

$result = ("$success"*100/"$all");
if ($result>100){
        $result = 100;
    }
$result = round($result);

$myfile = 'textfile.txt';
if (file_exists($myfile)) {
    echo "Файл $myfile существует";
} 

$myContent = $_POST['all'];
file_get_contents($myfile, utf8_encode($myContent)); 

$myfile2 = 'textfile2.txt';
$myContent2 = $_POST['success'];
file_get_contents($myfile2, utf8_encode($myContent2)); 

echo file_get_contents($myfile2);
?>

    <form action='http://content-available-to-author-only.do/index.php' method='post' >
    <fieldset>
     <input type="text" name='all' value="<?=$all;?>"><br>
    <input type="text" name='success' value="<?=$success;?>">
	<br>
	<button type="submit" class="btn">Результат</button>
    </fieldset>
    </form>

Проект
<div class="progress progress-info">
    <div class="bar" style="width: <?=$result;?>%"> <?=$success;?></div>
</div>