Empty fields can get inserted into my database - php

Question

I have the following code. I try to use my Submit button to insert the code into the database, but every time I use it and refresh the browser, empty fields get inserted into the database.
<?php
$servername = "localhost";
$username = "root";
$password = "";
//create connection
$cn = new mysqli($servername, $username, $password, "milege");
//check connection
if ($cn->connect_error) {
echo "Connection failed!". $cn->connect_error;
}
// once the button is clicked
if (isset($_POST['submitForm'])) {
//the values in the boxes
$name = $_POST['fname'];
$email = $_POST['email'];
$password = $_POST['password'];
$confpass = $_POST['confpass'];
$interest = $_POST['interest'];
$info = $_POST['info'];
//echo "connection successfully";
//Insert into table
$sql = "INSERT INTO miltb(name, email, password, interest, info, productorder) VALUES('$name', '$email', '$password', '$interest', '$info', 'none' )";
}
if ($cn->query($sql) == true) {
?><script>alert ("INSERTED SUCCESSFULLY!");</script><?php
} else {
echo "error: " . $sql . "\n" . $cn->error;
}
$cn->close();
?>
How would I fix it?

Answer 1

The reason empty fields get inserted in the database it's because you are not checking for empty fields, you need to check those empty fields first then if empty fields exists do not insert.
Well man there's a lot that you need to learn, you need to learn about
1.SQL Injections
2.mysqli prepared or pdo prepared statements.
3.Password hashing
Filter ,sanitize and validate user inputs
Never trust an input from the user, you must always treat a user input as if it comes from a dangerous hacker.
Then you code with prepared statements should look like this :
<?php
//create connection
$cn = new mysqli($servername, $username, $password, "milege");
//check connection
if ($cn->connect_error) {
echo "Connection failed!" . $cn->connect_error;
}
$error = "";
// once the button is clicked
if (isset($_POST['submitForm'])) {
// check for empty fiels
if (empty($_POST['fname'])) {
echo "Enter your name";
$error++;
} else {
$name = userInput($_POST['fname']);
}
if (isset($_POST['email'])) {
echo "enter email";
$error++;
} else {
$email = userInput($_POST['email']);
// validate email
if (!preg_match("/([\w\-]+\#[\w\-]+\.[\w\-]+)/", $email)) {
echo "enter a valid email";
$error++;
}
}
if (empty($_POST['password'])) {
echo "enter password";
$error++;
} else {
$password = userInput($_POST['password']);
$hash = password_hash($password, PASSWORS_DEFAULT); //hash the password
}
if (!empty($_POST['confpass']) && $_POST['confpass'] !== $_POST['password']) { //password confirmation
echo "passwords does not match";
$error++;
}
if (empty($_POST['interest'])) {
echo "enter interests";
$error++;
} else {
$interest = userInput($_POST['interest']);
}
if (empty($_POST['info'])) {
echo "enter info";
$error++;
} else {
$info = userInput($_POST['info']);
}
if ($error > 0) { // if we have errors don't insert to db
echo "you have " . $error . " error(s) on your form plz fix them";
} else { // no errors lets insert
// prepare and bind
$sql = $cn->prepare("INSERT INTO miltb(name, email, password, interest, info) VALUES (?, ?, ?,?,?)");
$sql->bind_param("sssss", $name, $email, $hash, $interest, $info);
if ($sql->execute()) {
echo "INSERTED SUCCESSFULLY!";
} else {
echo "could not insert ";
}
}
$sql->close();
$cn->close();
}
function userInput($data)
{
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>
Hope this will help and you will learn a thing or two, I stand to be corrected where I'm wrong

Answer 2

Use something like this to be sure values are inserted:
$name = isset($_POST['fname']) ? strval($_POST['fname']) : null;
if (empty($name)){
echo "Name can't be empty!";
exit();
}
Note: beware of SQL Injection. Using php function strval() is the least possible secutiry, but atleast use that, if nothing more.