<?php
  $file = "text.txt";
  @$fh = fopen($file, 'w') or die("can't open file");
  $data = "PHP is an open-source server-side scripting language.";
  fwrite($fh, $data);
  fclose($fh);
  echo "OK";
?>

<?php
  if (isset($_POST['submit'])) {
      $file = "config.php";
      @$fh = fopen($file, 'w') or die("can't open file");
     
      $host = $_POST['localhost'];
      $name = $_POST['dbname'];
      $user = $_POST['dbuser'];
      $pass = $_POST['dbpass'];
     
      $data = "<?php
\$localhost='$host';
\$dbname='$name';
\$dbuser='$user';
\$dbpass='$pass';
?>";
      fwrite($fh, $data);
      fclose($fh);
      echo "OK";
  } else {
     
?>
<form action="index.php" method="POST">
localhost:<input type=text name="localhost"<br>
dbname:<input type=text name="dbname"<br>
dbuser:<input type=text name="dbuser"<br>
dbpass:<input type=text name="dbpass"<br>
<input type="submit" name="submit" value="Submit">
</form>    
<?php
  }
?>