If session has value echo it else echo "all" - php

Question

Update 2
I'll just leave this here for future references. But this is the solution I created with all the help I got here. Thanks!
<script>
function Refresh() {
location.reload();
}
</script>
<?php $number = $_SESSION["page_id"]; ?>
<?php
if (isset($_SESSION['page_id']) && !empty($_SESSION['page_id'])) {
echo do_shortcode('[RICH_REVIEWS_SHOW category="page" num="all" id="'. $number .'"]');
session_destroy();
echo ('<button class="btn btn-0001" onclick="Refresh()">Show All</button>');
}
else{ echo do_shortcode('[RICH_REVIEWS_SHOW num="all"]'); }
;
?>
Update
So I'm trying to just do a simple echo to see if the session is set using this code:
<?php if(isset($_SESSION['page_id']) && !empty($_SESSION['page_id'])) {
echo 'Set and not empty, and no undefined index error!');
};?>
But doing this breaks my page, I just get a blank page? How do I check if the session is set? When I do a echo of the session using this code:
<?php echo $_SESSION["page_id"]; ?>
It does output the correct session value?? What am I doing wrong?
I have a sessions saved with PHP and I'm using this so that the page ID from Wordpress is echo-ed in a shortcode do_shortcode('');
This is what my code looks like:
<?php $number = $_SESSION["page_id"]; ?>
<?php echo do_shortcode('[RICH_REVIEWS_SHOW category="page" num="all" id="'. $number .'"]'); ?>
<?php echo do_shortcode_all('[RICH_REVIEWS_SHOW category="page" num="all" id="all"]'); ?>
<?php echo $shortcode ;?>
<?php echo $shortcode_all ;?>
Now, what I would like to do is IF the page_id is not stored in the session it should echo all. So how do I go about this?
I found this code, and I think its something I need... But I'm not that great a programmer/coder...
<?php
$var = 0;
// Evaluates to true because $var is empty
if (empty($var)) {
echo '$var is either 0, empty, or not set at all';
}
// Evaluates as true because $var is set
if (isset($var)) {
echo '$var is set even though it is empty';
}
?>
So, if I where to put these two together I would get something like this
<?php
$number = $_SESSION["page_id"];
// Evaluates to true because $var is empty
if (empty($number)) {
echo $shortcode_all ;
}
// Evaluates as true because $var is set
if (isset($number)) {
echo $shortcode ;
}
?>
Am I in the right direction?

Answer 1

Solution
<?php
if (isset($_SESSION['page_id']) && !empty($_SESSION['page_id'])) {
echo('Set and not empty, and no undefined index error!');
};
?>
What am I supposed to feel from the missing (?

Answer 2

If you are using wordpress then you should use the session_start(); in wp-config.php file so please first put in you wp-config.php at top and then check.

Answer 3

<?php
$number = $_SESSION["page_id"];
// Evaluates to true because $var is empty
if (empty($number) || $number=='') {
echo $shortcode_all ;
}else{
echo $shortcode ;
}
?>