程序运行截图如下：

源码如下： 

<?php
    $name =  "小明";
    $score = 88;

    if(is_int($score) || is_float($score)){

        if($score == 100){

            $str = "S级";
        }
        else if($score >= 90 && $score < 100){

            $str = "A级";
        }
        else if($score >= 80 && $score < 90){

            $str = "B级";
        }
        else if($score >=70 && $score < 80){

            $str = "C级";
        }
        else if($score >=60 && $score < 70){

            $str = "D级";
        }
        else if($score >= 0 && $score < 60){

            $str = "E级";
        }
        else{

            $str = "请输入0~100的数据";
        }
    }
    else{

        $str = "输入的数值格式不对";
    }
?>

<h2>学生成绩等级</h2>
<p>学生姓名: <?php echo $name ?></p>
<p>学生成绩: <?php echo $score ?></p>
<p>学生等级: <?php echo $str ?></p>