session_start(): Cannot send session cache limiter - headers already sent even with session_start() at the top [closed]

I'm trying to set up an admin login page but I keep getting this error. It works on a local server but not on an online server. I know this is a duplicate but all the other answer suggest putting session_start() at the top which I'm already doing. Here's my code

index.php

if ( !isset($_SESSION['user']) ){
header('Location: login.php');
} else {
?>
//html content
<?php
}


login.php (just html with a form tag)

<form method="POST" action="loginVerify.php" autocomplete="off">
<input type="text" name="username">
<input type="password" name="password">
<input type="submit" value="submit">
</form>


login verify

<?php
session_start();

$username = $_POST['username'];
$password = $_POST['password'];
$adminUsername = 'myUsername';
$adminPassword = 'myPassword';

if($username==$adminUsername && $password == $adminPassword) {
$_SESSION['user'] = $username;
header('Location: index.php');
} else {
header('Location: login.php');
}


Any ideas why this is happening? Also, is this a good structure for a login system? Am I doing this right?

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

login verify

index.php

if (

1 Answer
1

Add after any header('Location: xxx');.

header('Location: xxx');

command: die();

die();