<?php
$servername = "localhost";
$username = "root";
$password = "root";
$dbname = "databaze";

$name = mysqli_real_escape_string($connect, $_POST['name']);
$sex = mysqli_real_escape_string($connect, $_POST['sex']);

$name_2 = mysqli_real_escape_string($connect, $_POST['name_2']);
$sex_2 = mysqli_real_escape_string($connect, $_POST['sex_2']);

$conn = mysqli_connect($servername, $username, $password, $dbname);
if (!$conn) {
    die("Pripojeni selhalo: " . mysqli_connect_error());
}

$sql = "INSERT INTO uzivatele ($name, $sex)
VALUES ('name', 'sex');";
$sql .= "INSERT INTO uzivatele_2 ($name_2, $sex_2)
VALUES ('name_2', 'sex_2');";

if ($conn->multi_query($sql) === TRUE) {
    echo "Prihlaseni probehlo spravne";
} else {
    echo "Chyba: " . $sql . "<br>" . $conn->error;
}

mysqli_close($conn);
?>