Passing Drop Down Menu Value to CSV

I've got a form that has three drop down menus. In the html the options are named 0, 1 and 2 for validation purposes, and the actual inline text are the different options.

When I push the values to .csv, instead of having it just push the number, I wrote a few if statements to rename the variable that was saved. I've got it working, but rather than just have a bunch of if statements hanging around I thought I would slip them into a function and just call the function. However, when I do that, the value of whatever option the user selected reverts back to being stored as 0, 1 or 2 in the .csv file.

My question is what is my function missing that is causing it to only pick the numbered value?

HTML:

<select id="semesterSelector" name="semesterSelector" onchange="checkPage5()">
<option value="0">Select</option>
<option value="1">Fall</option>
<option value="2">Spring</option>
</select> 

PHP:

$semesterSelector = $_POST["semesterSelector"];

function semesterNameChange(){
if($semesterSelector == 1)
    {
        $semesterSelector = "Fall";
    }
    elseif($semesterSelector == 2)
        {
            $semesterSelector = "Spring";
        }
}
semesterNameChange();

Pushing the Value to Csv:

$csvData = [...] $semesterSelector [...]