PHP登录和重定向

Question

The following PHP code echoes error before entering mistaken password and gives - Notice: Undefined index: password

<?php 
    //Specify password here
    $pass='pass';
    if($_POST['password']!=$pass)
    {
        echo ("<div class='errmg'>Error</div>");
    }
    else
    {
        header( 'Location: admin.php' ) ;
    }
?>

Below I've the following HTML

<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
            Enter password:
            <input name="password" type="password">
            <input name="send" type="submit" value="Log in!">
        </form>

Please help me to repair these errors and make this login-redirect better

Answer 1

If you haven't submitted the form, $_POST is empty, so there's no $_POST['password'], just as the error says. Always check whether variables that may or may not be set exist before using them:

if (isset($_POST['password'])) {
    if ($_POST['password'] == $pass) {
        header(…);
    } else {
        // error
    }
}