PHP – setcookie() not working

Question

I have this page that sets a cookie and echos out a string if you check a checkbox. The string prints correctly, but the cookie never gets set and I have no idea why.

<form action="<?php echo $_SERVER['PHP_SELF'] ?>" method="post">
<label for="checkbox">Option 1:</label>
<input type="checkbox" name="checkbox" id="checkbox"><br>
<input type="submit" name="submit" value="Submit">
</form>
  <?php
if (isset($_POST['checkbox'])) {
  setcookie("cookie", "on", time()+3600*24);
  echo "You checked the checkbox and a cookie was set with a value of:<br>";
}
else {
  setcookie("cookie", "off", time()+3600*24);
  echo "You didn't check the checkbox and a cookie was set with a value of:<br>";
}
echo $_COOKIE['cookie'];
  ?>

Does anyone know why the above code does not work?

Answer 1

PHP superglobals are populated at script start-up time, and then are NOT modified or touched by PHP again for the life of the script. That means $_COOKIE represents the cookies that were sent to the server in the http request that fired up the script. It will NOT show any cookies you've added/changed/deleted during the life of the script. Those changes will only show up on the NEXT request.

The only exception to this is $_SESSION, which is populated when you call session_start().

If you need those values to be in $_COOKIE immediately, you'll have to add them manually, e.g.

setcookie('cookie', $value, ....);
$_COOKIE['cookie'] = $value;