<?php
$con = mysqli_connect("localhost:3306","id7390457_user","abcd1234","id7390457_data");

$username = $_POST["username"];
$password = $_POST["password"];

$statement = mysqli_prepare($con, "SELECT * FROM user WHERE username = ? AND password = ?");
mysqli_stmt_bind_param($statement, "ssis", $username, $password);
mysqli_stmt_execute($statement);

mysqli_stmt_store_result($statement);
mysqli_stmt_bind_result($statement, $user_id, $name, $age, $username, $password);

$response = array();
$response["success"] = false;

while(mysqli_stmt_fetch($statement)){
    $response["success"] = true;
    $response["name"] = $name;
    $response["age"] = $age;
    $response["username"] = $username;
    $response["password"] = $password;
}

echo json_encode($response);

<?php
$con = mysqli_connect("localhost", "id7390457_user", "abcd1234", "id7390457_data");

$name = $_POST["name"];
$age = $_POST["age"];
$username = $_POST["username"];
$password = $_POST["password"];
 $statement = mysqli_prepare($con, "INSERT INTO user (name, age, username, password) VALUES (?, ?, ?, ?)");
mysqli_stmt_bind_param($statement, "ssis", $name, $age, $username, $password);
mysqli_stmt_execute($statement);

$response = array();
$response["success"] = true;

echo json_encode($response);

$con = mysqli_connect("localhost", "id7390457_user", "abcd1234", "id7390457_data");