LetterGrades.php
<?php
		function checkGrade($Grade) {
		
			switch ($Grade) {
				case "A":
					echo "Your grade is excellent.";
					break;
				case "B":
					echo "Your grade is good.";
					break;
				case "C":
					echo "Your grade is fair.";
					break;
				case "D":
					echo "Your grade is passing.";
					break;
				case "F":
					echo "You failed.";
					break;
				default:
					echo "Invalid selection. Please select an A, B, C, D or F.";
					break;
			}
			
		}
		$Grade = $_GET["grade"];
		
?>



LetterGrades.html

    <form action="LetterGrades.php" method="get" >
  	  <p>Grade: <input type="text" name="grade" id="grade"/>
 	   <input type="submit" name="submit" id="submit"/></p>
    </form>