PHP会话变量不会改变

Question

UPDATE : I added all codes;

I want to create a login page for test purpose and I included attempt number with php sessions. The problem is session's variable isn't changing.

 index.php <?php if (!isset($_SESSION)) { session_start(); $_SESSION['attempt']=3; } if ($_SESSION['attempt']<0){ header('location:login_error.php'); } require('../function/start.php'); $title = 'Login'; require('../template/header.php'); $ip = !empty($_SERVER['HTTP_CLIENT_IP']) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : $_SERVER['REMOTE_ADDR']; var_dump($_SESSION['attempt']) ?> <h3 class="epad_header">Login</h3> <div id="epad_wrapper"> <div id="ad_form_wrapper"> <form action="control.php" method="POST"> <fieldset> <span class="formtext">ID</span> <input type="text" name="epadName" id="epadName" required> <span class="formtext">Pass</span> <input type="password" name="epadPass" id="epadPass" required> <input type="submit" value="Ok" class="formbuton" name="formbuton"> <br> <span class="formtext">IP Adress : <?php echo $ip; ?></span> <br> <span class="formtext">Attempt : <?php echo $_SESSION['attempt'] ?></span> </fieldset> </form> </div> </div> <?php require('../template/footer.php'); ?> 

 control.php <?php if (!isset($_SESSION)) { session_start(); } require('../function/start.php'); $title = 'Control'; if (isset($_POST['formbuton'])){ $name = htmlentities($_POST['epadName']); $pwd = htmlentities($_POST['epadPass']); } $check = $db->prepare('SELECT user, pass FROM users'); $check->execute(); $result = $check->fetch(PDO::FETCH_ASSOC); $user = $result['user']; $pass = $result['pass']; if ($name == $user && $pwd == $pass ){ $_SESSION['name']= $name; header("location:main.php"); }else{ $_SESSION['attempt']--; header('location:index.php'); } ?> 

• when a user enter the page(first visit) ; a session will be started, and attempt variable will be created. (index.php)

• If they enter false data attempt variable will be decreased. (control.php)

• if there are 3 failed attempt page will redirects to login_error.page (index.php)

First Problem : Session variable is not changing.

Second Problem: Even If I enter correct data, the page directs to index.php (login area) instead of main.php

Answer 1

try to place session_start(); at the first line, after <?php

Answer 2

I've solved the problem;

Actually I don't understand why

if(!isset($_SESSION){session_start; $_SESSION['attempt']=3;}

didn't work but when I modified this code to that code

session_start;
if (!isset($_SESSION['attempt']){$_SESSION['attempt']=3;}

Anyway, thank you for reading.