is there a function that will re-arramged the inputted names to last name?

this is what I coded and I'm still figuring out how to print the values on the if else statement using user defined function. And i need to put atleast three built-in functions to the code. in addition i do not have idea on how to print the inputted name from the user to lastname, firstname basis. i really need help

<?php

if (isset($_REQUEST['dulSubmit'])) {
    echo $_REQUEST['dulName'] . "of <b>" . $_REQUEST['dulYear'] . "-" . $_REQUEST['dulSet'] . "</b> <br> garnered <b>". $_REQUEST['dulGrade'] . "</b> grade or <b>" . $dulEquivGrade = $_REQUEST['dulGrade'] . "</b> <br> percentage equivalent in his/her <br/> <b>" . $_REQUEST['dulSub'] . "</b> subject"  ;


    $dulEquivGrade = $_REQUEST['dulGrade'];

    if ($dulEquivGrade >= 98  && $dulEquivGrade <=100) {
        return 1.00;
    
    } elseif ($dulEquivGrade >= 95 && $dulEquivGrade <=97 ) {
        return 1.25;
    } elseif ($dulEquivGrade >= 92 && $dulEquivGrade <=94) {
        return 1.50;
    }elseif ($dulEquivGrade >= 89 && $dulEquivGrade <=91) {
        return 1.75;
    } elseif ($dulEquivGrade >= 86 && $dulEquivGrade <=88) {
        return 2.00;
    } elseif ($dulEquivGrade >= 83 && $dulEquivGrade <=85) {
        return 2.25;
    } elseif ($dulEquivGrade >= 80 && $dulEquivGrade <=82) {
        return 2.50;
    } elseif ($dulEquivGrade >= 77 && $dulEquivGrade <=79) {
        return 2.75;
    } elseif ($dulEquivGrade >= 75 && $dulEquivGrade <=76) {
        return 3.00;
    } elseif ( $dulEquivGrade < 75) {
        return 5.00;
    }




}





  ?>