validation question
I have been working on a multi page form for my site. I got the functionality all working but now I was wondering how to validate that no fields are left blank during the process. Any help would be appreciated. I am using sessions to store my data
<?php
// Turn on sessions
session_start();
// Figure out what stage to use
if (($_SERVER["REQUEST_METHOD"] == "GET") || (! isset($_POST["stage"]))) {
$stage = 1;
} else {
$stage = (int) $_POST["stage"];
}
// Save any submitted data
if ($stage > 1) {
foreach ($_POST as $key => $value) {
$_SESSION[$key] = $value;
}
}
if ($stage == 1) { ?>
<form action="<?php echo $_SERVER["PHP_SELF"] ?>" method="post">
Name: <input type="text" name="name"/> <br/>
Age: <input type="text" name="age"/> <br/>
<input type="hidden" name="stage" value="<?php echo $stage + 1 ?>"/>
<input type="submit" value="Next"/>
</form>
<?php } else if ($stage == 2) { ?>
<form action="<?php echo $_SERVER["PHP_SELF"] ?>" method="post">
Favorite Color: <input type="text" name="color"/> <br/>
Favorite Food: <input type="text" name="food"/> <br/>
<input type="hidden" name="stage" value="<?php echo $stage + 1 ?>"/>
<input type="submit" value="Done"/>
</form>
<p>
<?php } else if ($stage == 3) { ?>
Hello <?php echo $_SESSION["name"] ?>.
You are <?php echo $_SESSION["age"] ?> years old.
Your favorite color is <?php echo $_SESSION["color"] ?>
and your favorite food is <?php echo $_SESSION["food"] ?>.
<?php } ?>