I need help updating user profile in PHP$.$

DBconnection.php:

load$()$;

$//$ Database configuration

$servername $=$ $$\_$ENV$[\text{'}$DB$\_$HOST'$]$;

$port $=$ $$\_$ENV$[\text{'}$DB$\_$PORT'$]$;

$username $=$ $$\_$ENV$[\text{'}$DB$\_$USER$\_$NAME'$]$;

$password $=$ $$\_$ENV$[\text{'}$DB$\_$PASSWORD'$]$;

$dbname $=$ $$\_$ENV$[\text{'}$DB$\text{'}]$;

$//$ Create connection

$this$->$conn $=$ new $\backslash$mysqli$($$servername, $username, $password, $dbname$)$;

$//$ Check connection

if $($$this$->$conn$->$connect$\_$error$)\{$

die$("$Connection failed: $".$ $this$->$conn$->$connect$\_$error$)$;

$\}$

$\}$

public function getConnection$()\{$

return $this$->$conn;

$\}$

public function closeConnection$()\{$

$this$->$conn$->$close$()$;

$\}$

$\}$

profile$\_$update.php:

query$($$sql$)$;

$row $=$ $result$->$fetch$\_$assoc$()$;

$//$ If the form is submitted

if $($$$\_$SERVER$["$REQUEST$\_$METHOD"$]==$ "POST"$)\{$

$//$ Get the new profile data from the form

$firstname $=$ $$\_$POST$[\text{'}$firstname$\text{'}]$;

$lastname $=$ $$\_$POST$[\text{'}$lastname$\text{'}]$;

$mobilenumber $=$ $$\_$POST$[\text{'}$mobilenumber$\text{'}]$;

$email $=$ $$\_$POST$[\text{'}$email$\text{'}]$;

$//$ Update the user's profile in the database

$sql $=$ "UPDATE Users SET firstname$=\text{'}$$firstname', lastname$=\text{'}$$lastname', mobilenumber$=\text{'}$$mobilenumber', email$=\text{'}$$email' WHERE id$=\text{'}$$id$\text{'}"$;

if $($$conn$->$query$($$sql$)===$ TRUE$)\{$

echo "Profile updated successfully";

$\}$ else $\{$

echo "Error updating profile: $".$ $conn$->$error;

$\}$

$\}$

$?>$