Please note that I want the compartment number to change.

<?php
    $compartment = "1";

        /* HERE I NEED SOME SCRIPT TO FIND THE EXTENSION OF THE FILE NAME $compartment AND TO SAVE THAT AS A VARIABLE NAMED 'EXTENSION'.*/

    if (file_exists($compartment.$extension)) {
        echo "$compartment.$extension exists!
    } else {
        echo "No file name exists that is called $compartment. Regardless of extension."
    }
?>


<?php
    $compartment = "2";

        /* HERE I NEED SOME SCRIPT TO FIND THE EXTENSION OF THE FILE NAME $compartment AND TO SAVE THAT AS A VARIABLE NAMED 'EXTENSION'.*/

    if (file_exists($$compartment.$extension)) {
        echo "$compartment.$extension exists!
    } else {
        echo "No file name exists that is called $compartment. Regardless of extension."
    }
?>

Thank You!