为什么我的PDO语句返回NULL？

Question

For some reason my PDO statement keeps returning NULL when it should return an integer. I've tried to directly input the query into my DB editor (HeidiSQL) and it works fine.

Here's the code:

                private function subscribe_moeder(){

                        $email = $this -> args["email"];

                        if(!filter_var($email, FILTER_VALIDATE_EMAIL))return $this -> errors[] = "Invalid email \n";


#                        /#  $Query = "SELECT * FROM subscribers WHERE email = :email";
#                       /##  $core = Core::getInstance();
#                      /###
#       This works    +####
#                      \###  $res = $core -> db -> prepare($Query);
#                       \##  $res -> bindParam(":email", $email);
#                        \#  $res -> execute();


                        if($found = $res -> fetch(PDO::FETCH_OBJ)){


#                           /#  $Query = "SELECT (SELECT id FROM subscriber_binaries WHERE name='møder') &
#                          /##           (SELECT attribute FROM subscribers WHERE email=:email) as s";
#                         /### 
#       This doesn't     +####  $res = $core -> db -> prepare($Query);
#                         \###  $res -> bindParam(":email", $email);
#                          \##  $res -> execute();
#                           \#  $s = $res -> fetch( PDO::FETCH_OBJ );

                                if($s -> s != 0){

                                        $this -> response = 'Already subscribed';

                                } else {

                                        $this -> response = $s->s;

                                }

                        }

                }

Answer 1

This is likely to be an encoding issue for the following reasons:

You select two values and do a binary conjunction. If the result is NULL then one of the operands must be NULL . Since the rear part will likely not be NULL , since the row exists (and I hope there is some value in the column), the front part must be NULL . There is a special Danish character in the query, I would therefore assume the row you want to select is not selected at all, making the query performing NULL & xxx , which evaluates to NULL .

Try to set the character set to UFT8 and also save your file as UTF8.

Also try to execute the first subquery from your sourcecode (not PMA) alone, to validate it returns what you expect.