Checking if an email exists in another table [duplicate] - php

Question

This question already has answers here:
How to check if a row exists in MySQL? (i.e. check if username or email exists in MySQL)
(4 answers)
Closed 2 years ago.
I'm doing an registration form and I'm trying to check if the email that the person inserts in the input is already in another table that has all emails that I allow to be registered. If it is it should register the person. I don't understand where I'm failing. I'm starting now with php. Please help.
<?php
if(isset($_POST['signup-submit'])){
require 'dbh.inc.php';
$username = mysqli_real_escape_string($conn, $_POST['uid']);
$email = mysqli_real_escape_string($conn,$_POST['mail']);
$password = mysqli_real_escape_string($conn,$_POST['pwd']);
$passwordRepeat = mysqli_real_escape_string($conn, $_POST['pwd-repeat']);
$check1 = $_POST['check1'];
$check2 = $_POST['check2'];
if(empty($username) || empty($email) || empty($password) || empty($passwordRepeat)) {
header ("Location: ../header.php?error=emptyfields&uid=".$username."&mail=".$email);
exit();
}
else if (!filter_var($email, FILTER_VALIDATE_EMAIL) && !preg_match("/^[a-zA-z0-9]*$/", $username)){
header("Location: ../header.php?error=invalidadmail&uid=");
exit();
}
else if (!filter_var($email, FILTER_VALIDATE_EMAIL)){
header("Location: ../header.php?error=invalidadmail&uid=".$username);
exit();
}
else if (!preg_match("/^[a-zA-z0-9]*$/", $username)){
header("Location: ../header.php?error=invalidaduid&mail=".$email);
exit();
}
elseif($password !== $passwordRepeat){
header("Location: ../header.php?error=passwordcheck&uid=".$username."&mail=".$email);
exit();
}
elseif((!isset($check1)) || (!isset($check2))){
echo"<script>alert('É necessário confirmar as duas opções :(');
window.location.href='../header.php'</script>";
exit();
}
This is the part of the code that is not working
$sql2 = "SELECT * FROM emails WHERE (email_socio = '$email')";
$res = mysqli_query($conn, $sql2);
if (mysqli_num_rows($res) < 0) {
echo "FAIL";
}
These are other validations and where it will insert the data into final table
else{
$sql = "SELECT uidUsers FROM users WHERE uidUsers=?";
$stmt = mysqli_stmt_init($conn);
if(!mysqli_stmt_prepare($stmt, $sql)){
header("Location: ../header.php?error=sqlerror");
exit();
}
else{
mysqli_stmt_bind_param($stmt, "s", $username);
mysqli_stmt_execute($stmt);
mysqli_stmt_store_result($stmt);
$resultCheck = mysqli_stmt_num_rows($stmt);
if($resultCheck > 0){
header("Location: ../header.php?error=usertaken&mail=".$email);
exit();
}
else {
$sql = "INSERT INTO users (uidUsers, emailUsers, pwdUsers) VALUES (?, ?, ?)";
$stmt = mysqli_stmt_init($conn);
if(!mysqli_stmt_prepare($stmt, $sql)){
header("Location: ../header.php?error=sqlerror");
exit();
} else {
$hashedPwd = password_hash($password, PASSWORD_DEFAULT);
mysqli_stmt_bind_param($stmt, "sss", $username, $email, $hashedPwd);
mysqli_stmt_execute($stmt);
$sql ="SELECT * FROM users WHERE uidUsers='$username' AND emailUsers='$email'";
$result = mysqli_query($conn, $sql);
if(mysqli_num_rows($result)>0){
while($row = mysqli_fetch_assoc($result)){
$userid = $row['idUsers'];
$sql = "INSERT INTO profileimg (userid, status) VALUES ('$userid', 1)";
mysqli_query($conn, $sql);
}
}
header("Location: ../header.php?signup=success");
exit();
}
}
}
}
mysqli_stmt_close($stmt);
mysqli_close($conn);
}
else {
header("Location: ../header.php");
exit();
}

Answer 1

Your condition is wrong:
if (mysqli_num_rows($res) < 0) {
echo "FAIL";
}
You're checking for less than zero, when in fact it should be less than one.
So, change it to either of the two:
if (mysqli_num_rows($res) === 0) // it logically cannot contain negative values
if (mysqli_num_rows($res) < 1)