-------------------------main.php (1 of 3)-------------------------------

<?php
require('dbc.inc.php');

$fn = 'Stefan';
$ln = 'Michael';
$u = 'bromelio';
$sn = '23';
$st = 'Stadlerweg';
$cit = 'Elsbethen';
$pc = '5061';
$ct = 'Austria';
$p = 'password1';
$sex = 'm';
$bd = '26';
$bm = '05';
$by = '1983';
$e = 'stefan.michael@hotmail.com';
$user_img = 'example.jpg';    
$pn = '00436504167777';

$q = "INSERT INTO users (username, email, pass, first_name, last_name, sex, birth_day, birth_month, birth_year, phone, street, street_nr, city, zip_code, country, user_img) VALUES ('$u', '$e', '$p', '$fn', '$ln', '$sex', '$bd', '$bm', '$by', '$pn', '$st', '$sn', '$cit', '$pc', '$ct', '$user_img')";
$r = mysqli_query($dbc, $q);

if (mysqli_affected_rows($dbc) === 1) { //that's where the problem occurs: in the Debugging -> variables window "affected_rows" correctly shows "1"...

echo 'Success';

}
else {
echo 'Error'; //...but stepping into (F7) once more it jumps to "-1" ending up echoing "Error" instead of "Success"
}

mysqli_close($dbc);

?>

---------------------included "dbc.inc.php" (2 of 3)-------------------------

<?php

// This file contains the database access information.
// This file establishes a connection to MySQL and selects the database.
// This file defines a function for making data safe to use in queries.
// This file defines a function for hashing passwords.
// This script is begun in Chapter 3.

// Set the database access information as constants:
DEFINE ('DB_USER', 'root');
DEFINE ('DB_PASSWORD', '');
DEFINE ('DB_HOST', 'localhost');
DEFINE ('DB_NAME', 'v');

// Make the connection:
$dbc = mysqli_connect (DB_HOST, DB_USER, DB_PASSWORD, DB_NAME) or die('Error connecting to MySQL server.');

// Set the character set:
mysqli_set_charset($dbc, 'utf8');

// Function for escaping and trimming form data.
// Takes one argument: the data to be treated (string).
// Returns the treated data (string).
function escape_data ($data, $dbc) {

// Strip the slashes if Magic Quotes is on:
if (get_magic_quotes_gpc()) $data = stripslashes($data);

// Apply trim() and mysqli_real_escape_string():
return mysqli_real_escape_string ($dbc, trim ($data));

} // End of the escape_data() function.

// Omit the closing PHP tag to avoid 'headers already sent' errors!