grading system php

<?php

function grading() {
    $accumulator = 0;
    for($i=0;$i<7;$i++){
        echo "Enter grade: ";
        $input = readline();
        if ($input>100 || $input<0) {
            echo "enter valid number! \n";
            $i-=1;
        }
        else {
            echo "Subject " . ($i+1) . ": " . $input . "\n";
            $accumulator+=$input;
        }

    }

    $average = $accumulator/7;

    echo "Average Grade: " . round($average, 2) . "\n";


    if ($average>=98 && $average<=100) {
        echo "With Highest Honor\n";
    }
    elseif ($average>=95 && $average<98) {
        echo "With High Honors\n";
    }
    elseif ($average>=90 && $average<95) {
        echo "With Honors\n";
    }
    elseif ($average>=75 && $average<90) {
        echo "Passed\n";
    }
    elseif ($average>=51 && $average<75) {
        echo "Failed\n";
    }
    echo "Continue?\n";
}
grading();
while(true){

    $input = readline();
   switch (strtolower($input)) {
       case 'no':
       case 'n':

           break 2;
       case 'yes':
       case 'y':
           grading();
           break;
        default:
            echo "Respond with either YES,Yes,yes or NO,No,no (or Y, y or N,n)\n";
            break;
   }

}

?>