Getting error: SQLSTATE[HY093]: Invalid parameter number: parameter was not defined - php

Question

I know what this error means, but I don't know why it is showing. I've checked names of variables, names of PDO variables, names of tables in database and still nothing.
If I copy insert into phpMyAdmin, it runs perfectly. If I change all variables from $this-> to 'abcd' it gives me the same error.
I really don't know what it is going on ...
Error:
SQLSTATE[HY093]: Invalid parameter number: parameter was not defined
Code:
class Users {
public $username = null;
public $password = null;
public $useremail = null;
public $steam_id = null;
public $salt = "Zo4rU5Z1YyKJAASY0PT6EUg7BBYdlEhPaNLuxAwU8lqu1ElzHv0Ri7EM6irpx5w";
public function __construct( $data = array() ) {
if( isset( $data['username'] ) ) $this->username = stripslashes( strip_tags( $data['username'] ) );
if( isset( $data['password'] ) ) $this->password = stripslashes( strip_tags( $data['password'] ) );
if( isset( $data['useremail'] ) ) $this->useremail = stripslashes( strip_tags( $data['useremail'] ) );
if( isset( $data['steam_id'] ) ) $this->steam_id = stripslashes( strip_tags( $data['steam_id'] ) );
}
public function storeFormValues( $params ) {
//store the parameters
$this->__construct( $params );
}
public function register() {
$correct = false;
try {
$con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
$sql1 = "SELECT * FROM users WHERE user_name = :username LIMIT 1";
$polacz1 = $con->prepare( $sql1 );
$polacz1->bindValue( "username", $this->username, PDO::PARAM_STR );
$polacz1->execute();
$row = $polacz1->fetch();
$sql2 = "SELECT * FROM users WHERE user_email = :useremail LIMIT 1";
$polacz2 = $con->prepare( $sql2 );
$polacz2->bindValue( "useremail", $this->useremail, PDO::PARAM_STR );
$polacz2->execute();
$row1 = $polacz2->fetch();
$sql3 = "SELECT * FROM users WHERE steam_id = :steam_id LIMIT 1";
$polacz3 = $con->prepare( $sql2 );
$polacz3->bindValue( "steam_id", $this->steam_id, PDO::PARAM_STR );
$polacz3->execute();
$row2 = $polacz3->fetch();
if($row == NULL){
if($row1 == NULL){
if($row1 == NULL){
$checksum = bin2hex(mcrypt_create_iv(22, MCRYPT_DEV_URANDOM));
$sql = "INSERT INTO users(user_name, user_email, user_pass, steam_id, email_hash) VALUES(:username, :useremail, :password, :steamid, :emailhash)";
$polacz = $con->prepare( $sql );
$polacz->bindValue( ":username", $this->username, PDO::PARAM_STR );
$polacz->bindValue( ":useremail", $this->useremail, PDO::PARAM_STR );
$polacz->bindValue( ":password", hash("sha256", $this->password . $this->salt), PDO::PARAM_STR );
$polacz->bindValue( ":steamid", $this->steam_id, PDO::PARAM_STR );
$polacz->bindValue( ":emailhash", $checksum, PDO::PARAM_STR );
$polacz->execute();
return '<div class="alert alert-success" role="alert">Zostałeś pomyślnie zarejestowany. Sprawdź podany adres email i aktywuj swoje konto!</div>';
//return "Rejestracja przebiegła pomyślnie, możesz się zalogować.";
} else return '<div class="alert alert-danger" role="alert">Podany steam ID już istnieje.</div>';
}
else
{
return '<div class="alert alert-danger" role="alert">Podany e-mail już istnieje.</div>';
}
}
else
{
return '<div class="alert alert-danger" role="alert">Podany użytkownik już istnieje.</div>';
}
}catch( PDOException $e ) {
return $e->getMessage();
}
}
}