switch范围判断

 <?php
 function grade($grade){
     switch (true) {
         case $grade>=90:
             echo 'A';
             break;
         case $grade>=80:
             echo 'B';
             break;
         case $grade>=70:
             echo 'C';
             break;
         case $grade>=60:
             echo 'D';
             break;
         default:
             echo 'E';
             break;
     }

 }
 grade(95);
 grade(85);
 grade(75);
 grade(65);
 grade(55);

 //ABCDE
 ?>