PDO DELETE also creates a new INSERT - php

Question

I have a strange problem where every time I do a simple DELETE query to delete WHERE email =. For some reason after deletion it also does a new INSERT with the same email? There is no INSERT anywhere and there are no triggers... Does anybody know why this happens? The table has a email and a nr with auto_increment.
$check_email = $_POST['email'];
$query = "SELECT `email` FROM `newsletter` WHERE email = '$check_email';";
$sth = $dbh->prepare($query);
$sth->execute();
$row = $sth->fetch(PDO::FETCH_ASSOC);
$check_users_email = $row['email'];
if($check_users_email != ''){
$query_update = "DELETE FROM `newsletter` WHERE email = '$check_users_email';";
}
$sth = $dbh->prepare($query_update);
$sth->execute();
Before deletion: email=test#email.com | nr=1
After deletion: email=test#email.com | nr=2

Answer 1

it might be in your sql string, since you're using prepared statements.
in PDO you should use named or unnamed placeholders. then after preparing the query, you pass the prams as an array when you execute the statement.
If you're using PDO, no need to use single quotes. just the column name and for the search value just use placeholders and then pass on the values on execution as an array.
NOTE: i renamed the PDO object $sth inside the 'if' statement, just to avoid name clash. also i moved the last 2 lines inside the 'if' statement, because you need the value of the sql string '$query_update' which will not be available if that statement returned false.
also to check if the variable $check_users_email is empty, you can use empty() or strlen().
try this:
$check_email = $_POST['email'];
$query = "SELECT email FROM newsletter WHERE email = :check_email";
$sth = $dbh->prepare($query);
$sth->execute(array(':check_email' => $check_email));
$row = $sth->fetch(PDO::FETCH_ASSOC);
$check_users_email = $row['email'];
if($check_users_email != ''){
$query_update = "DELETE FROM newsletter WHERE email = :check_users_email";
$sth2 = $dbh->prepare($query_update);
$sth2->execute(array(':check_users_email' => $check_users_email));
}