PHP - Fatal Error: Call To A Member Function Execute() On A Non-object

I'm new to coding and prepared statements.

I'm getting:
"Fatal error: Call to a member function bind_param() on a non-object in /home/content/01/3251001/html/Manage-Users/acc-files/updateRecord.php on line 17"

For this:

 <?php

include "db_connect.php"; 

if(isset($_POST['UserID'])){
	
	$stmt = $con -> prepare('UPDATE UserList 
		SET Status = ?,
			FirstName = ?,
			LastName = ?,
			Username = ?,
			Email = ?,
			Department = ?,
			Manager = ?,
		WHERE UserID = ?');

	$stmt -> bind_param('isssssss', /* Line 17 */
		$_POST['Status'],
		$_POST['FirstName'],
		$_POST['LastName'],
		$_POST['Username'],
		$_POST['Email'],
		$_POST['Department'],
		$_POST['Manager'],
		$_POST['UserID']);
	
	$stmt->execute();
}

Thank you in advance for helping.

I am trying to create a class and I ran into a problem. The connect function is returning a fatal error on the line below and I can't figure out the issue.

$result = $this->conn->query("SELECT unit FROM address");

class database {
	
	private	$server = "localhost";
	private	$db_user = "my user"; 
	private	$db_pass = "my pass"; 
	private	$db_name = "my database"; 
    private $conn;
	
	private $result = array(); 


	function connect(){
		// Create connection
		$this->conn = new mysqli($this->server, $this->db_user, $this->db_pass, $this->db_name);
		
		if ($this->conn->connect_error) {
			echo "Not connected, error: " . $mysqli_connection->connect_error;
		}
		else {
			//echo "Connected.";
			return $this->conn;
		}

	public function displayHeader(){
		$result = $this->conn->query("SELECT unit FROM address");

		if ($result->num_rows > 0) {
			// output data of each row
			while($row = $result->fetch_assoc()) {
				echo '<li>' . $row["unit"] . '</li>';
			}
		} else {
			echo "0 results";
		}
		$conn->close();
	}
		
	}

}

2 9 0 1

Fatal error: Call to a member function bind_param() on boolean.

It fails on the BIND_PARAM line.

I have looked at this all day, struggling with Mysqli as my normal MySql works fine with assoc and fetch.

I have verified in PhpInfo that mysqli is enabled.

I have verified its loaded using <?php print_r(get_loaded_extensions());

Added utf8 just to make sure. 

If I manually use the Wrong Password, I get a connection refused error, so I know its connected.

Verified my $_POST variables are there using Print in the 2 9 0 1 above.

All Table and Field Names are correct.  Manual Insert works fine in myPhpAdmin.

Tried Field Names and ? marks with and without single quotes.

All fields are Integers in the table.

Could it be related to an Auto_Increment Field in the table for a record ID that I am not providing??

A normal insert in myPhpAdmin doesn't need it.

        $QuestionID = $_POST['qID'];
        $PlayerID = $_POST['pID'];        
        $Answer = $_POST['ans'];
        $Option = $_POST['opt'];
        

        print $QuestionID . " ";
        print $PlayerID . " ";
        print $Answer . " ";
        print $Option . " ";

        $database = "Survey";

        $db_found = new mysqli('localhost', 'survey', 'survey', $database);
        $db_found->set_charset("utf8");
        
        if (!$db_found) {
            echo "Error: db connection = false";
        }
        else {
            $SQL_INSERT = "INSERT INTO 'Answers' ('QuestionID', 'PlayerID', 'Answer', 'Option') VALUES (?,?,?,?)";
            $stmt = $db_found->prepare($SQL_INSERT);
            $stmt->bind_param('iiii', $QuestionID, $PlayerID, $Answer, $Option);
            $stmt->execute();
        }

Thanks,

CadJoe

Hello everyone 
I am working on a simple php mysql project (TodoList with crud funtions with fields- head, content ,date and time ) and i am stuck on this error Fatal error: Uncaught Error: Call to a member function close() on bool Stack trace: #0 {main} 
How can i fix it 
Here is link from the project https://easyupload.io/gxxv1w
 

class User
    {  private $_db;
       
       public function __construct($user = null)
       {
          $this->_db = DB::getInstance();
           .......
       }
       public function find($user = null)
       { if($user)
         { $field = (is_numeric($user)) ? 'id' : 'username';
         $data = $this->_db->get('users', array($field, '=', $user));
           if($data->count())
           { .........
             return true;
           }
         }
         return false;
       }

public static function getInstance()
      { if(!(self::$_instance)): self::$_instance = new self();
        endif;
        return self::$_instance;
      }