Can'nt add data to MySQL with PHP - php

Question

I was trying to add a new user to the database with the next user id of last user's ID but its not happening.
function addNewUser($addUserName, $addUserEmail, $addUserPassword, $addUserAuthLevel){
$dbHost = "localhost";
$dbUser = "admin";
$dbPassword = "d4shb5w";
$dbName = "masterDatabase";
$connection = mysqli_connect($dbHost,$dbUser,$dbPassword, $dbName);
//test if connection occurred
if(mysqli_connect_errno()){
die("Database connection failed: " . mysqli_connect_error() . "(" . mysqli_connect_errno() . ")");
};
//adding new userInformation into database
$queryLastUserId = "SELECT * FROM userlogindetails ORDER BY userId DESC ";
$LastUserId = mysqli_query($connection, $queryLastUserId);
if($id=mysqli_fetch_assoc($LastUserId)){
$userId=$id["userId"]+1;
}
$userName = mysqli_real_escape_string($connection,$addUserName);
$userEmailId = mysqli_real_escape_string($connection,$addUserEmail);
$userPassword = $addUserPassword;
$passwordHash = password_hash($userPassword, PASSWORD_DEFAULT);
$userAuthLevel= $addUserAuthLevel;
$queryNewUser = "INSERT INTO userlogindetails(userId, userName, userEmailId, userPassword, userLoginTime, userAuthLevel) VALUE ($userId,'$userName', '$userEmailId', '$passwordHash', Now(),'$userAuthLevel')";
$result = mysqli_query($connection, $queryNewUser);
if($result){
mysqli_close($connection);
return "Success "/*.$userId*/;
}else{
mysqli_close($connection);
return "Failed "/*.$userId*/;
}
}
But when I assign usedId statically then it works fine.
What is the problem in the code?

Answer 1

Use the MAX function in a PHP function to get the value. This is a better practice.
function getMaxID($db){
$result = mysqli_query($db, "SELECT MAX(userId) FROM userlogindetails;");
return mysqli_fetch_assoc($result)["MAX(userId)"];
}
Note: I agree with the comments thus far: You should set the primary key to be auto-incrementing. That is an even better practice. MySQL workbench is a great (free) place to start, if you're not yet familiar with data structures.

Answer 2

All this can be done with simply making the id auto_increment in the database. Edit your table.

Answer 3

You need to assign a default value to your $userId variable (e.g. $userId = 1; at the beginning of the function).
If you don't initialize it and in your table there is no users your code will crash.