OOP: Function to check if value is in database - php

Question

I'm trying to create a user management system class and one of my functions is to check if a value is in a column in the database. It returns nothing at all.
Here is the relevant information:
require("opperators/connect.php");
class UserManagemen
{
protected $db;
public function __construct(PDO $db)
{
$this->db = $db;
}
public function isInDatabase($checkIfThis, $isHere)
{
$stmt = $db->prepare("SELECT 1 from users WHERE $isHere = :$isHere");
$stmt->execute(array(':$isHere' => $checkIfThis));
if ($stmt->rowCount() > 0) {
echo "It's in the database";
} else {
echo "Not in the database and you are good to go!";
}
}
}
$usermanagement = new UserManagemen($db, null, null, null);
$usermanagement->isInDatabase(Batman, username);
in connect.php: this worked in my procedural coding test.
$configurator['database'] = array(
'username' => 'root',
'password' => 'root',
'host' => 'localhost',
'db' => 'girlscouts',
);
$options = array(
PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8'
);
try {
$db = new PDO("mysql:host={$configurator['database']['host']};dbname={$configurator['database']['db']};charset=utf8", $configurator['database']['username'], $configurator['database']['password'], $options);
}
catch (PDOException $ex) {
die("Failed to connect to the database: " . $ex->getMessage());
}
I apologise in advance if this has been asked repeatedly, I've tried a google but returned nothing of value, possibly because I don't know what to google. I'm not big on asking for help but I'll give it a shot.

Answer 1

I think it should be
if ($stmt->rowCount() > 0) { // data available
echo "It's in the database";
} else {
echo "Not in the database and you are good to go!";
}
instead of
if ($stmt->rowCount() > 0) {
echo "Not in the database and you are good to go!";
} else {
echo "It's in the database";
}
Also you didn't initialize the PDO like new PDO(...);, in your constructor it should be
$this->db = new PDO(...);
and you should use it like
$stmt=$this->db->prepare(...);
$stmt->execute(...);
Take a look at this and this for details.

Answer 2

You are doing it wrong.
Instead of making additional request just to see, if such value already is stored in table, you should set UNIQUE constraint on column. Then, if you have correctly set up the PDO instance, the attempt to insert a duplicate will rise an PDOException, which then you can handle in whichever way you want.
Also the UNIQUE constraint would let you in MySQL perform .. ON DUPLICATE UPDATE .. construction.
To learn more about PDO use, read this tutorial. Seems like you are emulating the prepared statements.