Undefined index when no data entered - php

Question

Im working on a v2 of signing up.
I added some new input fields in various input types and the one that i use in v1 are now working properly, but the new ones don't. I noticed that it are only like the special input fields (checkboxes, selection menu, radio buttons, ...). I was testing out and when nothing is entered it just gives me this undefined index error (while i tried to define it). Note: the inputs that aren't working are not required fields!
Anyway, here is the PHP code:
// Initializing variables
$username = "";
$email = "";
$errors = array();
// Connect to the database
$conn = mysqli_connect($database['host'], $database['user'], $database['password'], $database['db'], $database['port']);
$email_show = $_POST['emailshow'];
// REGISTER USER
if (isset($_POST['reg_user'])) {
// Receive all input values from the form
$username = mysqli_real_escape_string($conn, $_POST['username']);
$email = mysqli_real_escape_string($conn, $_POST['email']);
$email_show = mysqli_real_escape_string($conn, $_POST['emailshow']);
$password_1 = mysqli_real_escape_string($conn, $_POST['password_1']);
$password_2 = mysqli_real_escape_string($conn, $_POST['password_2']);
$fname = mysqli_real_escape_string($conn, $_POST['fname']);
$fname_show = mysqli_real_escape_string($conn, $_POST['fnameshow']);
$lname = mysqli_real_escape_string($conn, $_POST['lname']);
$lname_show = mysqli_real_escape_string($conn, $_POST['lnameshow']);
$sex = mysqli_real_escape_string ($conn, $_POST['sex']);
$bday = mysqli_real_escape_string($conn, $_POST['bday']);
$country = mysqli_real_escape_string($conn, $_POST['country']);
$private_account = mysqli_real_escape_string($conn, $_POST['privateacc']);
$profile_style = mysqli_real_escape_string($conn, $_POST['profilestyle']);
// Form validation: ensure that the form is correctly filled ...
// By adding (array_push()) corresponding error unto $errors array
if (empty($username)) { array_push($errors, "Username is required"); }
if (empty($email)) { array_push($errors, "Email is required"); }
if (empty($password_1)) { array_push($errors, "Password is required"); }
if (empty($fname)) { array_push($errors, "Firstname is required"); }
if (empty($lname)) { array_push($errors, "Lastname is required"); }
if (empty($sex)) { array_push($errors, "What is your gender?"); }
if (empty($bday)) { array_push($errors, "When is your birthday?"); }
if (empty($_POST['country'])) { array_push($errors, "Test"); }
if ($password_1 != $password_2) {
array_push($errors, "The two passwords do not match");
}
HTML input:
<div class="box-title"><h1>Sign up</h1></div>
<div class="required-fields"><em>- Required fields are marked with *</em></div>
<div class="account-wrapper">
<div class="account-title">YOUR ACCOUNT</div>
<form method="post" class="accountform" action="/sign-up">
<input type="text" placeholder="Username*" name="username" onfocus="showDesc1()">
<div id="desc1">How others will see you <i id="close" onclick="closeDesc1()" class="fas fa-times-circle"></i></div>
<input type="email" placeholder="Email*" name="email" onfocus="showDesc2()">
<div id="desc2">We need this for important use <i id="close" onclick="closeDesc2()" class="fas fa-times-circle"></i><br><a style="color: blue;"> Read more (soon)</a></div>
<div id="emailshow"><input type="checkbox" id="emailshow-input" name="emailshow" value="showemail"><label style="text-decoration: underline;" data-tooltip="When this option is enabled, other users will be able to see your email on your profile." for="emailshow-input">Show on profile</label></div>
<input id="passwordfield" type="password" placeholder="Password*" name="password_1">
<div onclick="passwordVisb()" class="visb-innerhtml"><i id="visbcon" class="fas fa-eye"></i><label style="cursor: pointer;" id="visb-innerhtml"> Show password</label></div>
<input type="password" placeholder="Confirm password*" name="password_2" onfocus="showDesc3()">
<div id="desc3">Remember the entered password? <i id="close" onclick="closeDesc3()" class="fas fa-times-circle"></i></div>
</div>
</div>
<div class="details-wrapper">
<div class="details-title">YOUR DETAILS</div>
<div class="details-fields1">
<input type="text" placeholder="Firstname*" name="fname" onfocus="showDesc4()">
<div id="desc4">Your firstname <i id="close" onclick="closeDesc4()" class="fas fa-times-circle"></i></div>
<div id="fnameshow"><input type="checkbox" id="fnameshow-input" name="fnameshow" value="1"><label style="text-decoration: underline;" data-tooltip="When this option is enabled, other users will be able to see your firstname on your profile." for="fnameshow-input">Show on profile</label></div>
<input type="text" placeholder="Lastname*" name="lname" onfocus="showDesc5()">
<div id="desc5">Your lastname <i id="close" onclick="closeDesc5()" class="fas fa-times-circle"></i></div>
<div id="lnameshow"><input type="checkbox" id="lnameshow-input" name="lnameshow" value="1"><label style="text-decoration: underline;" data-tooltip="When this option is enabled, other users will be able to see your lastname on your profile." for="lnameshow-input">Show on profile</label></div>
<div class="gendersec">
<input id="genm" type="radio" name="sex" value="male">
<label for="genm">Male</label>
<input id="genf" type="radio" name="sex" required value="female">
<label for="genf">Female</label>
<input id="genc" type="radio" name="sex" value="custom">
<label for="genc" style="text-decoration: underline;" data-tooltip="Select this option if you do not want to tell us what your gender is or if you do have another gender not listed here." data-tooltip-location="top">Custom</label>
</div>
<input type="text" onkeypress="return false;" name="bday" autocomplete="off" placeholder="Birthday*" id="birthdaypicker">
</div>
<div class="details-fields2">
<?php include_once 'C:/xampp2/htdocs/includes/lang-select.php' ?>
<!-- <div id="tags-input">
<span>Socialhub</span>
<input type="text" disabled value="" placeholder="Interests (coming soon)">
</div> !-->
<p style="color: orange;">More options coming soon!</p>
</div>
</div>
<div class="settings-wrapper">
<div class="settings-title">QUICK SETTINGS</div>
<div class="settings-fields1">
<input type="checkbox" id="privateacc-input" name="privateacc" value="privateacctrue"><label for="privateacc-input" style="text-decoration: underline;" data-tooltip="If you enable this option, then the content of your account will be hidden for other users (they can still visit your account but they can't see the content). From your profile picture to your latest post will be hidden.">Private account</label>
<select class="profilestyle" name="profilestyle">
<option selected disabled>Select a style for your profile...</option>
<option value="default">Default (orange & green)</option>
<option value="red">Red</option>
<option value="black">Black</option>
<option disabled>These are coming soon for sure, stay tuned!</option>
<option disabled>Yellow</option>
<option disabled>Blue</option>
<option disabled>Pink</option>
<option disabled>...</option>
</select>
<p style="margin-top: 50px; color: orange;">More settings coming soon!</p>
</div>
</div>
<div class="bottom-wrapper">
<div class="bottom-topframe">
<i class="fas fa-arrow-left"></i> Nevermind!
<div class="agree-wrapper">
<input type="checkbox" id="agreetos-input" name="agreetos" value="tosagreed" onchange="document.getElementById('btnsubmit_reg').disabled = !this.checked;"><label for="agreetos-input">I agree with the Terms of Service (coming soon)</label>
<input type="checkbox" id="verifyage-input" name="verifyage" value="ageverified"><label for="verifyage-input">I am 13 years or older</label>
</div>
<input type="hidden" id="g-recaptcha-response" name="g-recaptcha-response">
<button type="submit" disabled name="reg_user" id="btnsubmit_reg" class="btnsubmit_reg">Sign up</button>
</div>
Thanks already. (Sorry for the search, big form)

Answer 1

This will help you, and like #Moayad .AlMoghrabi said you really should use better security also when it is local. Learn yourself always to write secure code.
$email = mysqli_real_escape_string($conn, $_POST['email']);
$email = isset($_POST['email']) ? mysqli_real_escape_string($conn, $_POST['email']) : '';
By checking your post values like this your variable will always have a value or a empty string.

Answer 2

I recommend you in order to fix this issue and to have more security as this code can be used in Mysql Injection easily, You have to escape all values from POST then you have to check if it is empty give it a default values.