我做错了什么？ “会话开始”

Question

The first code below should show random numbers between 10-400

The second code should show random numbers between 400-3000

If I use one code alone it will works correctly. But If I post both codes like this in one page the second code will work on the first code between 10-400.

What I'm doing wrong?

Here is my code:

<?php
session_start();
if(isset($_SESSION['num'])){
    $num = mt_rand($_SESSION['num']-5, $_SESSION['num']+5);
}else{
    $num = mt_rand(10, 400);
}
echo $num . " Gold coin"; 
$_SESSION['num'] = $num;
?>

---

<?php
session_start();
if(isset($_SESSION['num'])){
    $num = mt_rand($_SESSION['num']-5, $_SESSION['num']+5);
}else{
    $num = mt_rand(400, 3000);
}
echo $num . " Pink Coin"; 
$_SESSION['num'] = $num;
?>

Answer 1

It's because you're using the same session variable for both pieces of code, and after your first piece you set $_SESSION['num'] (which will be a value between 10 and 400), so the second piece of code will then take the first if branch and generate a value between the first value -5 and +5 (so it will be between 5 and 405). You should use different session variables for each coin type eg

session_start();
if(isset($_SESSION['gold'])){
    $gold= mt_rand($_SESSION['gold']-5, $_SESSION['gold']+5);
}else{
    $gold= mt_rand(10, 400);
}
echo $gold. " Gold coin"; 
$_SESSION['gold'] = $gold;
if(isset($_SESSION['pink'])){
    $pink= mt_rand($_SESSION['pink']-5, $_SESSION['pink']+5);
}else{
    $pink= mt_rand(10, 400);
}
echo $pink. " Pink coin"; 
$_SESSION['pink'] = $pink;

Note you should only call session_start() once.