table header does not change back after else clause

Question

I have a select with week numbers on my page, when I select a week number, the table header changes to the days in that specific week. When I want to display the whole month again (by selecting default in the week select) the header does not change for some reason. Here is my code:

function TableHeader($week, $month, $year){     
    if($week != "default")
    {
        for($i=1; $i<=7; $i++) 
        {
             $Datum = date('d', strtotime($year."W".$week.$i))."\n";
             echo "<th scope='col' id='CalendarTableHeader' style='text-align:center;'>".$Datum."</th>";
        }
    }
    else
    {
        for($i = 1; $i <= $numDays; $i++) 
            {
             echo "<th scope='col' id='CalendarTableHeader' style='text-align:center;'>".$i."</th>";
            }
    }
}

Other parts of code involved:

$numDays = monthDays($month, $year);

MonthDays function (working)

function monthDays($month, $year) {
    return date("t", strtotime($year . "-" . $month . "-01"));
}//

The part where I call the function (working)

if(isset($_GET['week'])){
    $week = $_GET['week'];
    TableHeader($week, $month, $year);
}

The strange part of my problem is that when I remove this part of my code out of my else clause:

for($i = 1; $i <= $numDays; $i++) 
{
    echo "<th scope='col' id='CalendarTableHeader' style='text-align:center;'>".$i."</th>";
}

It just works fine by itself.. I hope you can help me.

Answer 1

for($i = 1; $i <= $numDays; $i++) 
{
   echo "<th scope='col' id='CalendarTableHeader' style='text-align:center;'>".$i."</th>";
}

I did not find $numDays variable in your TableHeader function.

function TableHeader($week, $month, $year, $numDays) {
  // Your code here
}

I think it should be

$numDays = monthDays($month, $year);
if(isset($_GET['week'])){
    $week = $_GET['week'];
    TableHeader($week, $month, $year, $numDays);
}