mysqli update not updating although no error - php

Question

I am trying to adapt my code, which works in a SELECT, to perform an UPDATE. Here, there is no error, but it does not update anything, it even does not even enter the loop. It is supposed to update the room type for the chosen days ($value).
I echoed all values to check them up and they are correct.
$bdd = mysqli_connect('localhost', 'root', '', 'webpage')
$roomty = 1;
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
}
foreach ($_SESSION['datesBooked_1_month'] as $key => $value)
{
$stmt = mysqli_stmt_init($bdd);
if ( mysqli_stmt_prepare( $stmt , "UPDATE '".$_SESSION['tab_from_month_year']."'
SET '".$_SESSION['roomtype_x']."'='".$_SESSION['roomtype_x']."' + ? WHERE day = ?"))
{
mysqli_stmt_bind_param( $stmt ,'is', $roomty , $value );
mysqli_stmt_execute( $stmt );
mysqli_stmt_close($stmt);
echo " Booked !<br /> ";
}
}

Answer 1

Please try the following code with the new MySql driver of PHP.
you put the quote for a integer value, that is wrong
do you named column with numbers? That is not comfortable.
Are you sure that $value is a string?
Why did you use $key => $value in the foreach loop?
Here the code:
/* Connect to an ODBC database using driver invocation */
$dsn = 'mysql:dbname=webpage;host=127.0.0.1';
$user = 'root';
$password = 'dbpass'; #put here yor password
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
foreach $_SESSION['datesBooked_1_month'] as $value) {
#I hope that following variables don't contain space
$query = "UPDATE " .$_SESSION['tab_from_month_year'];
$temp = $_SESSION['roomtype_x'] + $roomty ;
#you wrote that $value is a string, are you sure?
$query .= " SET ".$_SESSION['roomtype_x']. "=$temp WHERE day='$value'" ;
$dbh->query($query);
}

Answer 2

I found out, the problem was the single quotes before the double quotes. It seems to be working very well with only double quotes like this :
if ( mysqli_stmt_prepare( $stmt , "UPDATE ".$_SESSION['tab_from_month_year']." SET ".$_SESSION['roomtype_x']." = ".$_SESSION['roomtype_x']." + ? WHERE day = ?"))

Answer 3

If this is the full code you need to select a database, currently the statement is being sent to the server but not to any database, there for you get no errors. You should use:
mysqli_select_db("You database goes here");