INSERT INTO SQL php Function does not work - php

Question

I have managed to write a php script that checks if a username already exists in the database and only adds a new user if it does not already exist.
This is my php script:
<?php
require "init.php";
if(isset($_POST['username']) && isset($_POST['forename']) && isset($_POST['surname']) && isset($_POST['password'])){
$username = $_POST['username'];
$forename = $_POST['forename'];
$username = $_POST['surname'];
$password = $_POST['password'];
$stmt = "SELECT username FROM users WHERE username = ?";
$result = $dbcon -> prepare($stmt);
$result->bind_param('s', $username);
$result->execute();
$result->bind_result($username);
if($result->fetch()){
echo "Can't add new user as it already exists!";
}
else{
$stmt_two = "INSERT INTO users (username, forename, surname, password)
VALUES(?, ?, ?, ?)";
$result_two = $dbcon -> prepare($stmt_two);
$result_two->bind_param('ssss', $username, $forename, $surname, $password);
$result_two->execute();
$result_two->close();
echo json_encode("Success");
}
}
?>
I believe the records are not being inserted or being inserted intermittently due to the fact that I have more than one prepared statement. If I just do the INSERT INTO statement on its' own with the SELECT FROM statement - the records are added almost instantly.
Why is this and what is wrong with my code?
Thanks

Answer 1

Just as I have said in the comments, don't over complicate and just check the number of rows found. No need to fetch anything. You're just checking if that user exists anyway.
$stmt = "SELECT username FROM users WHERE username = ?";
$result = $dbcon->prepare($stmt);
$result->bind_param('s', $username);
$result->execute();
$result->store_result();
if($result->num_rows() > 0) { // if it exists
} else {
// make your insertions
}
And another note:
isset can take multiple arguments:
if(isset($_POST['username'], $_POST['forename'], $_POST['surname'], $_POST['password'])) {
// and so on
}
Edit: Another flavor (using COUNT() of MySQL):
$stmt = "SELECT COUNT(username) FROM users WHERE username = ?";
$result = $dbcon->prepare($stmt);
$result->bind_param('s', $username);
$result->execute();
$result->bind_result($count);
$result->fetch();
if($count > 0) { // exists
} else {
// do something else
}