Пожалуйста помогите мой код вводит дубликаты записей

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<?php include('functionS.php');?>
<?php
	$username = "";
	$email = "";
	$errors = array();
	
	// connect to db
$db = mysqli_connect('localhost', 'root', '', 'registration');

	// when register button is clicked
if (isset($_POST['register'])) {
	$username = mysqli_real_escape_string($db,$_POST['username']);
		$email = mysqli_real_escape_string($db,$_POST['email']);
		$password_1 = mysqli_real_escape_string($db,$_POST['password_1']);
		$password_2 = mysqli_real_escape_string($db,$_POST['password_2']);
	
	//ensure that form fields are filled properly (validation)

		if(empty($username)){
		array_push($errors, "Username is required");
	}
		if(empty($email)){
		array_push($errors, "Email is required");
	}
		if(empty($password_1)){
		array_push($errors, "Password is required");
	}
		if($password_1 != $password_2){
		array_push($errors, "The two passwords do not match");

	}

	//if error free , save user to database

		if (count($errors) == 0){
			$password = md5($password_1); // encrypt password before storing in db(security)
			$sql = "INSERT INTO users (username, email, password)
			VALUES ('$username','$email','$password')";
	
			mysqli_query($db, $sql);
			$_SESSION['username'] = $username;
			$_SESSION['success'] = "You are now logged in";
			header('location: index.php');  // back to home page
	
	}
	}

	// log user in system

	if (isset($_POST['login'])){
		$username = mysqli_real_escape_string($db,$_POST['username']);
		$password = mysqli_real_escape_string($db,$_POST['password']);
	
	//ensure that form fields are filled properly (validation)

			if(empty($username)){
			array_push($errors, "Username is required");
	}
			if(empty($password)){
			array_push($errors, "Password is required");
	}	
			if (count($errors) == 0) {
				$password = md5($password);  // encrypt password before comparison
				$query = "Select * FROM users WHERE username = '$username' AND password = '$password'";
				$result = mysqli_query($db, $query);
	}
			if (mysqli_num_rows($result) == 1) {
		
	//log user in
			$_SESSION['username'] = $username;
			$_SESSION['success'] = "You are now logged in";
			header('location: index.php');  // back to home page
		
	}
	
	}

	// logout

	if (isset($_GET['logout'])) {
		session_destroy();
		unset($_SESSION['username']);
		header('location: login.php');
	}

	// register event
		
	if (isset($_POST['create_event'])) {
	
		$Event = mysqli_real_escape_string($db,$_POST['Event']);
		$Venue = mysqli_real_escape_string($db,$_POST['Venue']);
		$Host= mysqli_real_escape_string($db,$_POST['Host']);
		$Date = mysqli_real_escape_string($db,$_POST['Date']);
		$Start_time = mysqli_real_escape_string($db,$_POST['Start_time']);
		$Duration = mysqli_real_escape_string($db,$_POST['Duration']);
		$Entry_fee = mysqli_real_escape_string($db,$_POST['Entry_fee']);
		$Dress_code = mysqli_real_escape_string($db,$_POST['Dress_code']);
		$Ticket_purchase = mysqli_real_escape_string($db,$_POST['Ticket_purchase']);
		$Social_media_link = mysqli_real_escape_string($db,$_POST['Social_media_link']);
		
		//ensure that form fields are filled properly (validation)
	
		if(empty($Event)){
		array_push($errors, "Event is required");
	}
		if(empty($Venue)){
		array_push($errors, "Venue is required");
	}
		if(empty($Host)){
		array_push($errors, "Host is required");
	}
		if(empty($Date)){
		array_push($errors, "Date is required");
	}
	if(empty($Start_time)){
		array_push($errors, "Start_time is required");
	}
	if(empty($Duration)){
		array_push($errors, "Duration is required");
	}
	if(empty($Entry_fee)){
		array_push($errors, "Entry_fee is required");
	}
	if(empty($Dress_code)){
		array_push($errors, "Dress_code is required");
	}
	if(empty($Ticket_purchase)){
		array_push($errors, "Ticket_purchase is required");
		
	}
	if(empty($Social_media_link)){
		array_push($errors, "Social_media_link is required");
	}
	

	//if error free , save user to database

		if (count($errors) == 0){
			
			
			$sql1 = "INSERT INTO events (Event, Venue, Host, Date, Start_time, Duration, Entry_fee, Dress_code, Ticket_purchase, Social_media_link)
			VALUES ('$Event','$Venue','$Host','$Date','$Start_time','$Duration','$Entry_fee','$Dress_code','$Ticket_purchase','$Social_media_link')";
		$result = mysqli_query($db, $sql1);
		
		


		
	
			
	
	}
	}
	
	
?>

Что я уже пробовал:

игнорировать и заменять код

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