PHP & Unity - Moving Info back and forth - php

Question

I posted not long ago and decided to make another thread.
In our application we ask the players to create a new account, when they do we add this information to our DB.
The next step is to now grab the account they created, so that we can add more data to it. So the player creates an account with us, after this is done we then login with Google Play Services, and we now need to add info from google to the account they created, locale, id, etc
My problem here being new to php is im not sure on the correct way to do this so im asking for some guidance on it and have a couple of questions that may or may not make any sense.
When a user creates an account i now need to reference and keep a hold of this account they created so that we can easily access and edit/add info to it. How would you accomplish this?
When i need information from the database to display in the application how would i grab this info specific to the player and read it directly into unity? I think i could use the JsonEncode but im not sure if this is the most efficient way to do this.
There is more but i don't want to ask to much all at once haha.
Thanks for any and all help.
John
<?php
/// Check to make sure there is data in these fields
/// Only accept user when they have confirmed thier email
error_reporting('E_All');
include 'db_header.php';
$error = '';
$firstName = $_GET['firstName'];
$lastName = $_GET['lastName'];
$email = $_GET['email'];
$password = $_GET['password'];
$sql = "INSERT INTO Player (FirstName, LastName, Email, Password)
VALUES ('$firstName', '$lastName', '$email', '$password')";
// Here i need to make sure this is correct
if ($conn->query($sql) === TRUE)
{
$id = $conn->insert_id;
echo "Welcome " . $firstName . " You are now an Rcader! ";
}
else
{
//echo "Error: " . $sql . "<br>" . $conn->error;
$error = $conn->error;
echo $error;
}

Answer 1

First of all you should need to learn about the basic PHP and Unity3d integration through this simple unity3d Tut at unity wiki which is Server Side High Score.
Now come to your questions:
You should first authenticate user by asking user name and p/w in unity3d if his login is valid save its id/primary key into player prefs. Later use this player prefs value to store user specific information into database. You can also use this player prefs value to retrieve data from database. And never forget to remove player prefs values before exiting the game.