将递增的值存储在会话变量中并打印它

Had googled this but maybe I'm not a good googler. My ultimate goal is to have a view more button that will read the next 6 files from a directory but before I do that I need to figure out this problem:

at the top of my index.php i have this:

<?php
  if(session_id() == '') {
  session_start();
  $_SESSION["count"] = 0;
}
?>

lower down I have this:

<?php
function album() {
   $_SESSION["count"]=$_SESSION["count"]+10;
   echo $_SESSION["count"];
}
?>

when the user clicks a button its supposed to print the session variable + 10 on each click.. so 10 20 30 40 ..ect. But it keeps printing 10, it's not updating.

Always start session at the top of the page like

<?php 
session_start();

if(session_id() == '') {
  $_SESSION["count"] = 0;
}

function album() {
   $_SESSION["count"] += 10;
   echo $_SESSION["count"];
}


?>

You need to first do session_start() and then ask for $_SESSION.

<?php
  session_start();

  if(empty($_SESSION['count'])){
      $_SESSION["count"] = 0;
  }
  function album() {
       $_SESSION["count"] = $_SESSION["count"] + 10;
       echo 'Count: '.$_SESSION["count"];
  }
  album();

?>

This I just tested it and it works fine.