PHP How to implement flash messages - php

Question

I'm working on a small custom CMS and would like to implement flash messages. I have searched for hours, but I can't find anything that behaves the way I want. And I can't seem to make anything work.
I want to be able to pass a variable (via $_SESSION) to another page and, on that next request, it will be removed. I want to be able to use a keep_flash function, in case I don't want the message to be removed with the next server request.
Can anyone send me in the right direction? I can't really make anything work.
Thanks.
EDIT: Here is some code I am playing with. It sort-of works. When you first visit the page, it sets the $_SESSION and everything is fine. But if you refresh, now it deletes the $_SESSION. If you refresh again, it adds it back...etc. So, if you were to visit the page, refresh, then go to another page the flash message wouldn't be in the $_SESSION. So how can I fix this?
class flash
{
private $current = array();
private $keep = array();
public function __construct()
{
if (isset($_SESSION['flash'])) {
foreach($_SESSION['flash'] as $k=>$v)
{
$this->current[$k] = $v;
}
}
}
public function __destruct()
{
foreach ($this->current as $k=>$v)
{
if (array_key_exists($k,$this->keep) && $this->keep[$k] == $v) {
// keep flash
$_SESSION['flash'][$k] = $v;
} else {
// delete flash
unset($_SESSION['flash'][$k]);
unset($this->current[$k]);
unset($this->keep[$k]);
}
}
}
public function setFlash($key,$value)
{
$_SESSION['flash'][$key] = $value;
}
public function keepFlash($key)
{
$this->keep[$key] = $this->getFlash($key);
}
public function getFlash($key)
{
if (array_key_exists($key,$this->current)) return $this->current[$key];
return null;
}
}

Answer 1

basic idea is to have script always check specific variable in session (usually called 'flash') for content - if not empty display and delete it from session. When message is needed just place is same variable in session and next check would pick it up....
keep_flash in your case would not proceed with delete, or move to other place based on your needs.
for implementation just google it - usually it wrapped in some kind of class - I personally like phpclasses.org or part of framework