Hidden Fields

A hidden field is form control that is not displayed to the user. As such, it can be used to hold a value that acts as state on a web page and allows values to persist between multiple calls to web pages. In the example below, we have a simple integer value that is stored in _POST['i'] and incremented each time the submit button is pressed.

Of course, pressing the submit button refreshes the entire page as well as incrementing the value.

Hidden.php

<html>
<head><title>Hidden Fields</title></head>
<body>

<?php
  if (!isset($_POST['i'])) {
    $_POST['i'] = 1;
  } else {
    ++$_POST['i'];
  }
?>

<form action="Hidden.php" method="post">
<p><?php echo $_POST['i'] ?></p>
<input type = "hidden" name="i" value="<?php echo $_POST['i'] ?>" />
<input type="submit" />
</form>

</body>
</html>

Core PHP

Hidden Fields

Hidden.php

Output