courseGrade.php

<?php

class courseGrade
{

	public function grade($currentGrade)
	{

		if (!is_integer($currentGrade)) {
			return "Invalid Data";
		}

		if ($currentGrade < 60) {
			return "Try again";
		}

		if ($currentGrade > 100) {
			return "Value No Valid";
		}

		if ($currentGrade >= 70 and $currentGrade < 80) {
			return 'Well';
		}

		if ($currentGrade >= 80 and $currentGrade < 90) {
			return "Very good";
		}

		if ($currentGrade >= 90 and $currentGrade <= 100) {
			return "Satisfying";
		}

		if ($currentGrade >= 60 and $currentGrade < 70) {
			return "Enough";
		}

	}

}

$currentGrade = 65;

$newGrade = new courseGrade();

echo $newGrade->grade($currentGrade);