why doesn't it want to check and then insert - php

Question

for school i have to make a portfolio with a working login and registration system, the login part kinda works but by the regestration part i kinda got stuck. so why doesn't want to insert the users data after it checks the database of the username and email already exists? (hope u dont mind, but i am still a student who recently started with coding)
<?php
include_once 'db_connect.php';
include_once 'psl-config.php';
$error_msg = "";
if (isset($_POST['username'], $_POST['email'], $_POST['p'])) {
$username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
$email = filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL);
$email = filter_var($email, FILTER_VALIDATE_EMAIL);
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$error_msg .= '<p class="error">The email address you entered is not valid!</p>';
}
$password = filter_input(INPUT_POST, 'p', FILTER_SANITIZE_STRING);
if (strlen($password) != 128) {
$error_msg .= '<p class="error">Invalid password configuration.</p>';
}
$query_username = "SELECT id
FROM members
Where username == '$username'
LIMIT 1";
$available_username = array();
if ($resultUsername = mysqli_query($mysqli, $query_username)) {
if (mysqli_num_rows($resultUsername) > 0) {
$error_msg .= '<p class="error">A user with this username already exists!</p>';
}
}
$query_email = "SELECT id
FROM members
Where email == '$email'
LIMIT 1";
$available_email = array();
if ($resultEmail = mysqli_query($mysqli, $query_email)) {
if (mysqli_num_rows($resultEmail) > 0) {
$error_msg .= '<p class="error">A user with this email adress already exists!</p>';
}
}
if (empty($error_msg)) {
$ipadress = $_SERVER['REMOTE_ADDR'];
$random_salt = hash('sha512', uniqid(openssl_random_pseudo_bytes(16), TRUE));
$password = hash('sha512', $password . $random_salt);
if (!$tableRowEmail = 1) {
$sqlinsert = "INSERT INTO members (username, email, ipadress, password, salt) VALUES ($username, $email, $ipadress, $password, $random_salt)";
if (!mysqli_query($mysqli, $sqlinsert)) {
header('Location: ../error.php?err=Registration failure: INSERT');
}
}
header('Location: ./register_success.php');
}
}
?>

Answer 1

Just a wild guess: You use == in your sql statements. I'm quite sure you should only use =

Answer 2

Field values are missing single quote '
all the fields are varchar datatype.Single quotes should be used for string values.
$sqlinsert = "INSERT INTO members (username, email, ipadress, password, salt) VALUES ('$username', '$email', '$ipadress', '$password', '$random_salt')";