can't insert into database (webservice) - php

Question

I am creating a web service which will be called from an android app. Actually I am trying to do an insert into my database but i can't figure out why it is not working. Here is my code, with some tests I have made in order to find the bug :
<?php
$con = mysqli_connect("localhost", "xxx", "xxx", "xxx");
/* here is the original code that I commented in order to do my tests
$mail = $_POST["mail"];
$mdp = $_POST["mdp"];
$nom = $_POST["nom"];
$prenom = $_POST["prenom"];
$dateNaissance = $_POST["dateNaissance"];
*/
$mail = "test#mail.fr";
$mdp = "test";
$nom = "test";
$prenom = "test";
$dateNaissance = "2000/01/01";
$statement = mysqli_prepare($con, "INSERT INTO utilisateur (mail, mdp, nom, prenom, dateNaissance) VALUES (?, ?, ?, ?, ?)");
mysqli_stmt_bind_param($statement, "sssss", $mail, $mdp, $nom, $prenom, $dateNaissance);
mysqli_stmt_execute($statement);
$query = "SELECT * FROM utilisateur";
$result2 = mysqli_query($con, $query);
$final = mysqli_fetch_row($result2);
print_r($final);
?>
The SELECT request returns me the row I have in my utilisateur table so I suppose it's not a problem of connection.
Moreover, mysqli_stmt_execute($statement) returns 1... So if i'm not wrong it's supposed to mean that my request worked ? Anyway, nothing is inserted.
I'm hosting my database with 000webhost, don't know if this will help... I'm starting developing so everything is not crystal clear.
Hope that I was understandable and that you'll enlighten me!

Answer 1

I found what was wrong : everything was working really well... But i was connecting to the wrong database. Indeed I began my project in localhost and then used 000webhost hosting. I got confused since it was written "server : localhost" in the two phpMyAdmin interfaces and also because I had the exact same table in the two databases.
Thanks for the answers that still made me learn.

Answer 2

The query causes this error
Error: Field 'idUser' doesn't have a default value.
You will need to fix your table. Make it an InnoDB table.
CREATE TABLE `utilisateur` (
`idUser` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
`mail` VARCHAR(40) COLLATE utf8_bin NOT NULL,
`mdp` VARCHAR(40) COLLATE utf8_bin DEFAULT NULL,
`nom` VARCHAR(40) COLLATE utf8_bin DEFAULT NULL,
`prenom` VARCHAR(30) COLLATE utf8_bin DEFAULT NULL,
`dateNaissance` DATE DEFAULT NULL,
PRIMARY KEY (`idUser`)
) ENGINE=INNODB DEFAULT CHARSET=utf8;