How to insert data into MySQL using MySQLi? - php

Question

I am new to using MySQLi. I try to use MySQLi in order to insert data in my database. But does not work. Where may be the error?
echo 'connected';
$con = mysqli_connect("localhost",$username,$password,$database);
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
// mysqli_select_db($con,"kraus");
$firstname = $_POST['uname'];
$lastname = $_POST['address'];
$age = $_POST['pass'];
$sql = "INSERT INTO registration('uname', 'address', 'password') VALUES ('$firstname', '$lastname', '$age')";
mysqli_query($con,$sql);
echo "1 record added";
mysqli_close($con);

Answer 1

Why is line this commented out? You are selecting the database in mysqli_connect("localhost","root","root","kraus") but it makes no sense why that is there:
// mysqli_select_db($con,"kraus");
Should you not have that commented like this?
mysqli_select_db($con,"kraus");
Also there is no space here between registration and the fields in (…) as well as the quotes around your fields:
$sql = "INSERT INTO registration('uname', 'address', 'password') VALUES ('$firstname', '$lastname', '$age')";
That should be like the following with a space added between the table name & the fields. And since there should just be no quotes around your field names so the final query should be this:
$sql = "INSERT INTO registration (uname, address, password) VALUES ('$firstname', '$lastname', '$age')";
Or perhaps have back ticks like this:
$sql = "INSERT INTO registration (`uname`, `address`, `password`) VALUES ('$firstname', '$lastname', '$age')";
Also, you should really refactor & cleanup your whole codebase like this:
// Set the connection or die returning an error.
$con = mysqli_connect("localhost","root","root","kraus") or die(mysqli_connect_errno());
echo 'connected';
// Select the database.
// mysqli_select_db($con, "kraus");
$post_array = array('uname','address','pass');
foreach ($post_array as $post_key => $post_value) {
$$post_key = isset($_POST[$post_value]) && !empty($_POST[$post_value]) ? $_POST[$post_value] : null;
}
// Set the query.
$sql = "INSERT INTO registration (uname, address, password) VALUES (?, ?, ?)";
// Bind the params.
mysqli_stmt_bind_param($sql, 'sss', $uname, $address, $pass);
// Run the query.
$result = mysqli_query($con, $sql) or die(mysqli_connect_errno());
// Free the result set.
mysqli_free_result($result);
// Close the connection.
mysqli_close($con);
echo "1 record added";
Note how I am using mysqli_stmt_bind_param and also setting an array of $_POST values & rolling throughout them. Doing those two basic things at least enforce some basic validation on your input data before it gets to the database.

Answer 2

You have quotes around the column names in your query. Maybe you meant to use backticks instead:
(`uname1`, `address`,...)
You are also vulnerable to sql injection. Look into mysqli prepared statements.