User registration form not working as it such php - php

Question

I have create a form with html and php that allows a user to create an account and their information is stored within a mysql database.
The forms works and the user is able to create an account. However if the user clicks the submit button without filling in the form it seems to display that the email address has already been added.
I can't seem to see what is wrong.
My php code
<?php
session_start();
error_reporting(E_ALL); ini_set('display_errors', 1);
include "connect.php";
if (isset($_POST["submit"])) {
$error = array(); // Declare An Array to store any error message
$title = $_POST['title'];
$address2 = $_POST['up_address2'];
if(empty($_POST['up_first_name'])) { // if no name has been supplied
$error[] = 'Please Enter Your First Name'; // add to array "error"
} else {
$firstName = $_POST['up_first_name']; // else assign it to a variable
}
if(empty($_POST['up_last_name'])) { // if no name has been supplied
$error[] = 'Please Enter Your Last Name'; // add to array "error"
} else {
$lastName = $_POST['up_last_name']; // else assign it to a variable
}
if(empty($_POST['up_email'])) { // if no name has been supplied
$error[] = 'Please Enter Your Email'; // add to array "error"
} else {
if (preg_match("/^([a-zA-Z0-9])+([a-zA-Z0-9\._-])*#([a-zA-Z0-9_-])+([a-zA-Z0-9\._-]+)+$/", $_POST['up_email'])) {
// regular expression for email validation
$email = $_POST['up_email'];
} else {
$error[] = 'Your email is invalid';
}
}
if(empty($_POST['up_password'])) {
$error[] = 'Please Enter Your Password';
} else {
$password = $_POST['up_password'];
}
if(empty($_POST['up_date_of_birth'])) {
$error[] = 'Please Enter Your Date Of Birth';
} else {
$dateOfBirth = $_POST['up_date_of_birth'];
}
if(empty($_POST['up_number'])) {
$error[] = 'Please Enter Your Contact Number';
} else {
$number = $_POST['up_number'];
}
if(empty($_POST['up_address'])) {
$error[] = 'Please Enter Your First Line of Your Address';
} else {
$address = $_POST['up_address'];
}
if(empty($_POST['up_country'])) {
$error[] = 'Please Enter Your Home Country';
} else {
$country = $_POST['up_country'];
}
if(empty($_POST['up_postcode'])) {
$error[] = 'Please Enter Your Postcode';
} else {
$postcode = $_POST['up_postcode'];
}
if(empty($error)) // send to Database if there's no error
{
// If everything is ok...
// Make sure the email address is avilable:
$query_verify_email = "SELECT * FROM user WHERE Email ='$email'";
$result_verify_email = mysqli_query($con, $query_verify_email);
if(!$result_verify_email) {
echo 'Database Error Occured';
}
if (mysqli_num_rows($result_verify_email) == 0) { // IF no previous user is using this email.
$query_insert_user = "INSERT INTO user (Title, FirstName, LastName, Email, Password, DataOfBirth, ContactNumber, Address, Address2, Country, Postcode)VALUES ('$title', '$firstName', '$lastName', '$email', '$password', '$dateOfBirth', '$number', '$address', '$address2', '$country', '$postcode')";
$result_insert_user = mysqli_query($con, $query_insert_user);
if (!$result_insert_user) {
echo 'Query Failed ';
}
} else { // If it did not run OK.
echo '<div class="errormsgbox">You could not be registered due to a system </div>';
}
} else { // The email address is not available.
echo '<div class="errormsgbox" >That email address has already been registered.</div>';
}
}
?>
My html form
<form name="signup" id="signup" action="create_account.php" method="post">
<label for="title">Title</label>
<select name="title" id="title">
<option value="Mr">Mr</option>
<option value="Miss">Miss</option>
<option value="Mrs">Mrs</option>
<option value="Ms">Ms</option>
<option value="Dr">Dr</option>
</select>
<br>
<label for="up_first_name">First Name</label>
<input type="text" name="up_first_name" id="up_first_name" placeholder="First Name" />
<br>
<label for="up_last_name">Last Name</label>
<input type="text" name="up_last_name" id="up_last_name" placeholder="Last Name" />
<br>
<label for="up_email"> Email</label>
<input type="email" name="up_email" id="up_email" placeholder="username#email.com" />
<br>
<label for="up_password">Password</label>
<input type="password" name="up_password" id="up_password" placeholder="Password" />
<br>
<label for="up_date_of_birth">Date Of Birth</label>
<input type="text" name="up_date_of_birth" id="up_date_of_birth" placeholder="dd/mm/yyyy" />
<br>
<label for="up_number">Contact Number</label>
<input type="text" name="up_number" id="up_number" placeholder="[phone]" />
<br>
<label for="up_address">Address</label>
<input type="text" name="up_address" id="up_address" placeholder="Address" />
<br>
<label for="up_address2">Address 2 (optional)</label>
<input type="text" name="up_address2" id="up_address2" placeholder="Address 2" />
<br>
<label for="up_country">Country</label>
<input type="text" name="up_country" id="up_country" placeholder="Address 2" />
<br>
<label for="up_postcode">Postcode</label>
<input type="text" name="up_postcode" id="up_postcode" placeholder="Postcode" />
<br>
<input id="submit" name="submit" type="submit" value="Register My Account" id="myButton" class="btn btn-primary"/>
</form>