Saving Form Data into a Cookie in PHP

After the form has been submitted, the data must be stored somewhere i.e. in a database, in a file, or sent via email. When a website contains several similar forms (for example, forms requiring the user to provide his name and contact information), it is a good idea to save the data after the user fills it in. Because HTTP is a stateless protocol, you have to use cookies.

Saving Data into a Cookie

<?php
 function saveFormData($post) {
  $keys = implode('-;-', array_keys($post) );
  $vals = implode('-;-', array_values($post) );
  $data = "$keys:;:$vals";
  
  $expire = time() + 86400 * 30; //30 days 
  setcookie('data',$data, $expire, '/', 'brainbell.com');
 }

Because user agents only have to save 20 cookies per domain, it’s a good idea to store the form information in one cookie, in the form of an array. But, only string values are allowed in cookies; this is why you have to convert the $_POST array into a string.

The function getCookieData() retrieves the existing data from the cookie and converts it into an array and returns it (or returns false if data is unavailable):

<?php
 function getCookieData() {
  if (! isset($_COOKIE['data']) )
   return false;
  $data = explode(':;:', $_COOKIE['data']);
  $keys = explode('-;-', $data[0]);
  $vals = explode('-;-', $data[1]);
  return array_combine($keys, $vals);
 }

The only thing left to do is to write the required form data into this array. You can specifically submit only certain values or the complete array $_GET or $_POST, as shown in the following code.

Saving (and retrieving) form data in a cookie:

<?php
 if ($_SERVER['REQUEST_METHOD'] == 'POST') {
  saveFormData( $_POST );
 }
 else {
  printForm();
 }

 function saveFormData($post) {
  $keys = implode('-;-', array_keys($post) );
  $vals = implode('-;-', array_values($post) );
  $data = "$keys:;:$vals";
  
  $expire = time() + 86400 * 30; //30 days 
  setcookie('data',$data, $expire, '/');
  echo '<h1>Form Saved in a Cookie</h1>
        <p><a href="example.php">Go back</a></p>';	 
 }
 function getFormData() {
  if (! isset($_COOKIE['data']) )
   return false;
  $data = explode(':;:', $_COOKIE['data']);
  $keys = explode('-;-', $data[0]);
  $vals = explode('-;-', $data[1]);
  return array_combine($keys, $vals);
 }
 function printForm(){
  $data = getFormData();
  if ($data === false){
   echo '<p><b>You\'ve previously not submitted the form.</b></p>';
  }
  else{
   echo '<p><b>Your previously submitted values:</b></p>';
   echo '<pre>';
   print_r($data);
   echo '</pre>';
  }
  ?>
<form method="post" action="">
 <div>Name: <input type="text" name="name"></div>
 <div>Email: <input type="email" name="email"></div>
 <input type="submit" name="submit" value="Submit">
</form>
  <?php
 }

Figure shows the resulting cookie:

Processing Forms in PHP: