如何使用PHP将php变量从下拉列表传递到另一个下拉列表？

 
  
 
  Toggle navigation     Student Scheduling System 
  
 
 
 
  Home 
 
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Student
 
 
 Student List 
  
 
   <?php $result = mysql_query("Select tbl_course.studno, tbl_course.studfname, tbl_course.studlname, tbl_coursetype.course_desc, tblyear.YearName, tblset.setname, tblset.ID from tbl_course, tbl_coursetype, tblyear, tblset where tbl_coursetype.course_no=tbl_course.studcourse AND tblyear.ID=tbl_course.studyear AND tblset.ID=tbl_course.studset", $connection); if (!$result) { die("Database query failed: " . mysql_error()); } // 4. Use returned data while ($row = mysql_fetch_array($result)) { echo ""; echo ""; echo ""; echo ""; echo ""; echo ""; echo ""; echo ""; echo ""; echo ""; echo ""; echo ""; } ?>  
 
 
 
Student ID
 
First Name
 
Last Name
 
Course
 
Year
 
Section
 
Section ID
 
 
 
".$row[0]."
".$row[1]."
".$row[2]."
".$row[3]."
".$row[4]."
".$row[5]."
".$row[6]."
View Subject
 
 
  
  
   Add Student   
 
 
 
 × 
Add new student
 
 
 
 
 First Name  
 
 Last Name  
 
 Student Course   <?php $result = mysql_query("Select setcours, course_desc from tblset, tbl_coursetype where tbl_coursetype.course_no=tblset.setcours group by setcours", $connection); if (!$result) { die("Database query failed: " . mysql_error()); } // 4. Use returned data while ($row = mysql_fetch_array($result)) { echo "{$row[1]}"; } ?>  
 
 Student Year   <?php $result = mysql_query("Select setyear, YearName from tblset, tblyear where tblyear.ID=tblset.setyear group by setyear", $connection); if (!$result) { die("Database query failed: " . mysql_error()); } // 4. Use returned data while ($row = mysql_fetch_array($result)) { echo "{$row[1]}"; } ?>  
 
 Section   <?php $result = mysql_query("SELECT * FROM tblset t LIMIT 0,1000", $connection); if (!$result) { die("Database query failed: " . mysql_error()); } // 4. Use returned data while ($row = mysql_fetch_array($result)) { echo "{$row[1]}"; } ?>  
 
 
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– 以上是整个代码。 以下是截图。

我很困惑，因为BSIT只有第一年水平，但每当我选择BSIT时，第二次下降也会出现第3年水平，这是第3年仅适用于BSED。 简而言之，我希望每当我选择一个课程时，它会自动更改第二个下拉菜单及其相应的年级/ s。 我为此感到抱歉，但我只是想知道它是否可能以及如何实现？ 如果可以，请教我。 谢谢！

Answer 1

就像我在评论中建议的那样，你可以使用chainedjs ，或者你可以创建自己的函数，如：

 $( document ).ready(function() { $('#select1').on("change", function(){ var selectedClass = $(this).val(); //store the selected value $('#select2').val(""); //clear the second dropdown selected value //now loop through the 2nd dropdown, hide the unwanted options $('#select2 option').each(function () { var newValue = $(this).attr('class'); if (selectedClass != newValue && selectedClass != "") { $(this).hide(); } else{$(this).show(); } }); }); }); 

    number 1 number 2    number 1.1 number 2.1 number 1.2 number 2.3 number 1.3 number 1.2