PHP - 10 Counting Before Number 2

Folks,

Having trouble here. Forgot how you use the COUNT. Not interested in the num_rows due to it being slow compared to COUNT.

I have users table like this:

id|username|sponsor_username

0|barand|requinix

1|phpsane|alison

2|mickey_mouse|requinix

Now, I want to check if a sponsor username exists or not. Such as does the entry "requinix" exists or not in one of the rows in the "sponsor_username" column.

In our example it does twice and so the variable $sponsor_username_count should hold the value "2". Else hold "0".

I get error:

Fatal error: Uncaught mysqli_sql_exception: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '?' at line 1 

My code:

	$stmt_1 = mysqli_prepare($conn,"SELECT COUNT(sponsor_username) from users = ?"); 
            mysqli_stmt_bind_param($stmt_1,'s',$sponsor_username_count); 
            mysqli_stmt_execute($stmt_1); 
            
            //Show error if 'users' tbl was not successfully queried". 
            if (!$stmt_1) 
            { 
                echo "ERROR 1: Sorry! Our system is currently experiencing a problem loading this page!"; 
                exit(); 
            } 
            else 
            { 
                mysqli_stmt_bind_result($stmt_1,$sponsor_username_count);     
                mysqli_stmt_fetch($stmt_1); 
                mysqli_stmt_close($stmt_1); 
                
                //Check if Sponsor Username in Url ($_GET) is already registered or not. If not then show "Invalid Url" or Link message. 
                if ($sponsor_username_count < 1) 
                { 
                    echo "<b>Invalid Url or Link!<br> Invalid Sponsor: \"$sponsor_username\"!</b><?php "; 
                    exit(); 
                } 
            } 
	

|  id          | int(4)       | NO   | PRI | NULL    | auto_increment |
| user_id     | int(4)       | NO   |     | NULL    |                |
| recipient   | varchar(30)  | NO   |     | NULL    |                |
| subject     | varchar(25)  | YES  |     | NULL    |                |
| cc_email    | varchar(30)  | YES  |     | NULL    |                |
| reply       | varchar(20)  | YES  |     | NULL    |                |
| location    | varchar(50)  | YES  |     | NULL    |                |
| stationery  | varchar(40)  | YES  |     | NULL    |                |
| ink_color   | varchar(12)  | YES  |     | NULL    |                |
| fontchosen  | varchar(30)  | YES  |     | NULL    |                |
| message     | varchar(500) | NO   |     | NULL    |                |
| attachment  | varchar(40)  | YES  |     | NULL    |                |
| messageDate | datetime     | YES  |     | NULL    |        

            $params = array(                 
               ':user_id' => $userid,                 
               ':recipient' => $this->message_vars['recipient'],                 
               ':subject' => $this->message_vars['subject'],                 
               ':cc_email' => $this->message_vars['cc_email'],                 
               ':reply' => $this->message_vars['reply'],                 
               ':location' => $this->message_vars['location'],                 
               ':stationery' => $this->message_vars['stationery'],                 
               ':ink_color' => $this->message_vars['ink_color'],                 
               ':fontchosen' => $this->message_vars['fontchosen'],                 
               ':message' => $messageInput,                 
               ':attachment' => $this->message_vars['attachment'],                 
               ':messageDate' => $date             );

$sql = "INSERT INTO messages (user_id,recipient, subject, cc_email, reply, location,stationery, ink_color, fontchosen, message,attachment) VALUES( $userid, :recipient, :subject, :cc_email, :reply, :location, :stationery, :ink_color, :fontchosen, $messageInput, :attachment, $date);";

And lastly, here is how I am calling it:
            $dbh = parent::$dbh;             
           $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);              
           if (empty($dbh))    return false;             
                  $stmt = $dbh->prepare($sql);             
                 $stmt->execute($params) or die(print_r($stmt->errorInfo(), true));              
           if (!$stmt) {    print_r($dbh->errorInfo());              }