php check duplicate email string - php

Question

I've got small problem checking the duplicate email, I don't know what I've done wrong.
PHP SIDE:
// convert to lower case
$email = $db->real_escape_string(trim(strtolower($_POST['email'])));
$q = $db->query("SELECT email FROM user WHERE email='$email'");
$r = $q->fetch_assoc();
if($email == $r['email']) {
echo 'yes';
} else {
echo 'no';
}
I've got an old record in the database. Some of the emails come mixed with uppercase and lowercase! And most of them are from hotmail email account! How to check email that even contain lower and uppercase?
ie: Donald1990#hotmail.com // it skips the duplicate error?
Hedmunds#hotmail.co.uk
hedmunds#hotmail.co.uk

Answer 1

Actually I think you want
"SELECT LOWER(email) FROM user WHERE LOWER(email)='$email'"

Answer 2

i am using laravel 5, but the concept is same
//check from 1 to 500 records, some DB will timeout if 1 to 5000 or more depends on amount of Data, you may have to increase the timeout limit
$users = Subscribers::all(); // take all users from DB
for ($x = $check_from; $x <= $check_to; $x++){
$check_user = Subscribers::select('id','email')->where('id',$x)->first();
if (!isset($check_user)){ // check for gaps in betw records
echo $x . "- not set<br>";
}
else{
$check_user_id = strtolower(trim($check_user->id));
$check_user_email = strtolower(trim($check_user->email));
foreach ($users as $user){
$user_id = strtolower(trim($user->id));
$user_email = strtolower(trim($user->email));
if ($check_user_email == $user_email AND $check_user_id !== $user_id ){
echo $check_user_id.' - '.$user_id.' - '. $user_email.' - Duplicated records<br>';
//$user->delete();
// choose to delete duplicate or whatever u wanna do with it
}
}
}
}
// need to check email is equal && user_id is not same, then there will be 2 id with same email
My code works but if someone can improve to make it shorter will be better.