How would I go by checking if email is already in use? - php

Question

I have been working on my account creation page and I am stuck onto where I should be checking if email is already in use and how to go by it. would I need to make a query statement like this
Select * from Customers WHERE Email = $email)
and check that way?
<?php
session_start();
?>
<?php require_once("headerTH.html") ?>
<?php
$db= new PDO("sqlite:onlinestore.db");
if(ISSET($_POST['register'])){
$username = $_POST['username'];
$email = $_POST['email'];
$psw = sha1($_POST ['psw']);
$tel = $_POST['tel'];
if(! empty($email) && !empty($psw)) {
$query = "INSERT INTO Customers (UserName, Passwd, PhoneNumber, Email) VALUES(:UserName, :Passwd, :PhoneNumber, :Email)";
$result = $db->prepare($query);
$result->bindParam(":UserName", $username);
$result->bindParam(":Passwd", $psw);
$result->bindParam(":Email", $email);
$result->bindParam(":PhoneNumber", $tel);
// Account pass or fail
if($result->execute()){
echo"You have successfully created an account.{$_POST['email']}<br>";
}else{
///print_r($db->errorInfo());
require_once("create.php");
}
} else {
echo "all fields are required";
require_once("create.php");
}
} else {
require_once("create.php");
}
?>
<?php require_once("footerT.html")?>

Answer 1

I think the ideal way to do this is to check if the new email exists in the database, and based on that situation. The user will be able to create the account if the new email doesn't exist in the database, otherwise you should show an alert that email already exists.

Answer 2

Just required a simple if statment at the top
$stmt = $db->prepare("SELECT * FROM Customers WHERE Email=?");
$stmt->execute([$email]);
$user = $stmt->fetch();
if($user){
//email found
echo "Email already used";
}else if($result->execute()){
echo"You have successfully created an account.{$_POST['email']}<br>";
}else{
///print_r($db->errorInfo());
require_once("create.php");
}
} else {
echo "all fields are required";
require_once("create.php");
}
}

Answer 3

If it's me, YES, like what you said, I create a new function let say function checkUserByEmail($email) to check if the email already exists or not.
Then again you can use the same function if you need to check the user by email, let say at the time of login (if you using email for login).
By the way, DON't FORGET TO SANITIZE YOUR INPUTS ;)