Preserve Data When Going Back

[rsmith]

Probably a simple question. One of my forms does some checking to make sure required fields are filled out. If they're not, the script halts, alerts the user, and gives them a link to go back and correct the problem. My issue is that when they click the link or use the back button the form is empty again. What's the best way to go about resolving this?

[NogDog]

If you are using sessions (or can add sessions to your application), you could store the values in the $SESSION array. Then have your form check to see if the values exist, e.g.:

<input type="text" name="example" value="<?php
echo (isset($_SESSION['example'])) ? htmlentities($_SESSION['example'], ENT_QUOTES) : '';
?>" />

Another technique is to use the same script for both displaying and processing the form. Then via use of if/else conditions you can choose whether or not to display the form, using the same technique as above for displaying values but using the $_POST array (or $GET if the get method was used) instead of the $SESSION array.

<?php
if(isset($_POST['some_field'])
{
   // validate form, save error messages in $error array, then...
   if($isValid)
   {
      // process results, then...
      header('http://www.example.com/thank_you.php');
      exit;
   }
}
?>
<!-- input form -->
<?php
if(!empty($errors))
{
   echo "<p class='error'>" . implode(' ', $error) . "</p>\n";
?>
<form action='<?php echo $_SERVER['PHP_SELF']; ?>' method='post'>
<input type="text" name="example" value="<?php
echo (isset($_POST['example'])) ? htmlentities($_POST['example'], ENT_QUOTES) : '';
?>" />
</form>