MySQL PHP Matching User ID's when creating a "USER" - php

Question

I am coding a "social media site" for a class project, and I am having trouble in one section.
When first registering an account, the user must enter a username and password, and click a submit button. PHP code checks the inputs to make sure they're all valid and that there will not be any duplicates, and if everything passes, it adds in the username and password into a SQL table called "users". Users has 3 columns: username, password, and userID. userID is the primary key.
Once that process is completed, we redirect to a separate page, where the user can enter more personal information, such as first and last name, city, country, etc. This table, called "userInfo" has the columns: firstName, lastName, emailAddress, address, city, country, and userID. userID, once again, is the primary key.
What I'm trying to figure out is how to match the two user ID's in an insert statement. I have a form that gathers all the required information, but I am not sure how to set up the SQL query to make sure that users.userID matches userInfo.userID.
Here's my PHP for users (initial registration)
<?php
session_start();
require_once('dbConnect.php');
$error = "false";
$errorMessage = "";
if(isset($_POST['submit'])){
// Get inputs
$username = $_POST['user'];
$password = $_POST['password'];
// Clean inputs and encrypt password
$username = mysqli_real_escape_string($conn, $username);
$password = mysqli_real_escape_string($conn, $password);
$password = md5($password);
// Check username not empty
if (empty($username)) {
$error = "true";
$errorMessage = "Please enter a value for your username";
}
// Check username does not already exist
$checkUserQuery = "SELECT username FROM users WHERE username = '$username'";
$checkResult = $conn->query($checkUserQuery);
if($checkResult->num_rows > 0) {
$error = "true";
$errorMessage = "This username already exists";
}
// Username does not exist, add to database
else {
$insertUserQuery = "INSERT INTO users (username, password) VALUES('$username', '$password')";
$insertResult = $conn->query($insertUserQuery);
$_SESSION['username'] = $username;
header("Location: userInfo.php");
}
}
?>
Here's my PHP code so far for userInfo:
<?php
session_start();
require_once('dbConnect.php');
$error = "false";
$errorMessage = "";
$username = $_SESSION['username'];
if(isset($_POST['submit'])){
// Get inputs
$firstName = $_POST['firstName'];
$lastName = $_POST['lastName'];
$emailAddress = "fakeEmailAddress#fakeyfakefake.com";
$address = $_POST['address'];
$city = $_POST['city'];
$country = $_POST['country'];
// Clean inputs
$firstName = mysqli_real_escape_string($conn, $firstName);
$lastName = mysqli_real_escape_string($conn, $lastName);
$address = mysqli_real_escape_string($conn, $address);
$city = mysqli_real_escape_string($conn, $city);
$country = mysqli_real_escape_string($conn, $country);
// Validate Inputs (Only validating first and last name, location entries are not required)
if(empty($firstName) || empty($lastName)) {
$error = "true";
$errorMessage = "Please enter your first AND last name";
}
else {
}
}
?>
Apologies if this is super messy. Databases are NOT my strong suit lol.
Many thanks to anyone who can help!

Answer 1

You'll want to get the mysqli_insert_id for your insert into the users table and pass that along (potentially via your $_SESSION) for creation in userInfo.