PHP-使用sha1哈希密码的登录功能，无法使其正常工作

Question

for a college project I need to create a simple registration and login function. We are required to hash the password using sha1 (I know its not secure), and add a specific salt at the start of the password. Data is being stored in a mySQL database. The registration.php seems to be working out, but I'm having trouble comparing the password from the html form to the password stored in the database. Been googling for a day now, but I am only finding login-functions using the password_verify() function, which doesn't seem to work with sha1. Apologies if the solution or obvious, VERY new to php.

Didn't include my connection-part of the code, it's working as intended. no matter what I input in the fields in the html-form, I get the "invalid username or password" output no matter what.

$formUsername = mysqli_real_escape_string($connect, $_REQUEST['username']);
$formPassword = mysqli_real_escape_string($connect, $_REQUEST['password']);


$sql = "SELECT passord FROM bruker WHERE brukerNavn = '$formUsername';";
$passwordFraDatabase = mysqli_query($connect, $sql);


$row = mysqli_fetch_assoc($passwordFraDatabase);
$passordSomString = $row['passord'];


$salt = 'IT2_2018';
$passwordFraForm = sha1($salt . $formPassword);

if ($passwordFraForm == $passordSomString) {
    echo("Logged in");
}
else echo("invalid username or password");

---

Edit: To those saying I shouldn't use sha1, read the entire question, I specifically said I was required to use sha1, its a college project. Since someone asked, this is how the password is registered in the first place:

$email = mysqli_real_escape_string($connect, $_REQUEST['email']);
$username = mysqli_real_escape_string($connect, $_REQUEST['username']);
$password = mysqli_real_escape_string($connect, $_REQUEST['password']);


$salt = 'IT2_2018';
$securepassword = sha1($salt . $password);

$sql = "INSERT INTO bruker (ePost, brukerNavn, passord) VALUES ('$email', '$username', '$securepassword')";
if(mysqli_query($connect, $sql)){
    echo "user registered!";
} else{
    echo "could not register user " . mysqli_error($connect);
}

Answer 1

In Php default compare function (strcmp) and (==) operator both can compare maximum of 32bit character string. So more than 32bit character string must be compared using (strncmp) function.

In your case as you using sha1 which producing 160bit string thats why it is not working. So use strncmp(str1,str2,maximum_length_want_to_compare);

In your case it will be

if (strncmp($passwordFraForm, $passordSomString,160)==0){ echo("Logged in"); } else echo("invalid username or password");