database

<?php
if (isset($_POST[1]) && isset($_POST[2]) && isset($_POST[3]) && isset($_POST[4])) {

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "database";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

$sql = "SELECT eMail FROM dero";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        //echo "id: " . $row["eMail"];
        if ($row["eMail"] == $_POST[2]) {
          echo '<script>
          document.getElementById("r_passw_error").innerHTML="↻ un account con questa mail esiste gia";
          $("#r_passw").blur (function (e){document.getElementById("r_passw_error").innerHTML=""});
          </script>';

        } else {
              $query = "INSERT INTO dero (user, eMail, Password) VALUES ('$_POST[1]','$_POST[2]','$_POST[3]')";
              $result = mysqli_query($conn, $query);
              if (!$result) {
              die("errore nella qery $query:");}
              echo '<p style ="color: red;">tutto funziona per il meglio</p>';

        }
    }
}
}
?>