Email validation MySQL and PHP - email

Question

I want to check if email already exists in the DB, starting at this and need some help. Here is the code:
<?php
require_once('includes/connects.php');
$username = $_POST['username'];
$nome = $_POST['nome'];
$password = sha1($_POST['password']);
$email = $_POST['email'];
$checkmail = mysql_query("SELECT email FROM utilizadores WHERE email = '$email'");
$result = $conn->query($checkmail);
if($result->num_rows == 0){
$querygo = "INSERT INTO utilizadores (username, nome, password, email) VALUES ('$username', '$nome', '$password', '$email'";
$result = $conn->query($querygo);
header('Location: index.php');
} else {
echo 'DONT WORK';
}
This is the error:
Fatal error: Call to a member function query() on a non-object in
C:\Sites\deca_13L4\deca_13L4_23\MiniProjeto\bussaco\registo.php on
line 12 Warning: Unknown: 1 result set(s) not freed. Use
mysql_free_result to free result sets which were requested using
mysql_query() in Unknown on line 0

Answer 1

Looking at your code, unsure what value this has in the mix of everything since that is exactly where the error occurs:
$result = $conn->query($checkmail);
So I would change your code to be like this:
<?php
require_once('includes/connects.php');
$username = $_POST['username'];
$nome = $_POST['nome'];
$password = sha1($_POST['password']);
$email = $_POST['email'];
$checkmail = mysql_query("SELECT email FROM utilizadores WHERE email = '$email'");
if(!$checkmail){
$querygo = "INSERT INTO utilizadores (username, nome, password, email) VALUES ('$username', '$nome', '$password', '$email'";
$result = $conn->query($querygo);
header('Location: index.php');
} else {
echo 'DONT WORK';
}
But that said, it’s unclear to me where the actual needed mysql_connect comes from. Is that in require_once('includes/connects.php');? I hope so. Otherwise mysql_query won’t work no matter what. To execute a query you need a connection.

Answer 2

just make your code as simple as you can. So here:
<?php
require_once('includes/connects.php');
$username = $_POST['username'];
$nome = $_POST['nome'];
$password = sha1($_POST['password']);
$email = $_POST['email'];
$checkmail = mysql_query("SELECT email FROM utilizadores WHERE email = '$email'");
$num_rows = mysql_num_rows($checkmail);
if($num_rows){
$querygo = "INSERT INTO utilizadores (username, nome, password, email) VALUES ('$username', '$nome', '$password', '$email'";
$result = mysql_query($querygo);
header('Location: index.php');
} else {
echo 'DONT WORK';
}