根据另一个下拉列表填充下拉列表的最佳和最简单的方法是什么 [英] What's the best and easiest way to Populate a dropdown based on another dropdown
问题描述
很简单，我有一个动态填充数据的下拉菜单:
Very simply, I have one dropdown menu dynamically populated with data:
SQL 代码
$querycourse = "SELECT course, COUNT(course) AS count FROM acme WHERE course IS NOT NULL GROUP BY course ";
$procc = mysqli_prepare($link, $querycourse);
$queryc = mysqli_query($link, $querycourse) or die(mysqli_error($link));
PHP 代码
echo "<select name='course[]' value='' multiple='multiple' size=10>";
// printing the list box select command
echo "<option value=''>All</option>";
while($ntc=mysqli_fetch_array($queryc)){//Array or records stored in $nt
echo "<option value="$ntc[course]">"$ntc[course]"</option>";
/* Option values are added by looping through the array */
}
echo "</select>";// Closing of list box
我需要的是另一个下拉列表，其中填充了基于第一个下拉框中选择的数据.
What I need is another dropdown that is populated with data based on a selection from the first dropdown box.
我正在使用 MySQL、PHP、Javascript，也可以(一推)使用 jQuery.我没有使用 Ajax 的经验.
I am using MySQL, PHP, Javascript and can also (at a push) use jQuery. I have no experience in Ajax.
有人愿意为我指出正确的方向吗?！
Would anyone be kind enough to point me in the right direction?!
提前致谢，一如既往，
荷马.
推荐答案
第一种和最好的方法(如果您有或可能有足够的选项特定数据)
使用 AJAX.我认为，与其他实现相同的方法相比，这是最简单的方法.使用Jquery 实现AJAX.它让 AJAX 变得轻而易举！在这里，我为你分享我的一块蛋糕 -
First and Best Method (If you have or may have enough option specific data)
Use AJAX. It is the easiest way, I think, compared to the other ways to implement the same. Use Jquery to implement AJAX. It makes AJAX a piece of cake! Here I share my piece of cake for you -
以下是您需要的大致完整代码 -
Following is roughly the complete code you need -
像这样在您的第一个选择中调用一个 javascript 函数 populateSecondDropdown() -
Call a javascript function populateSecondDropdown() on your first select like this -
echo "<select name='course[]' value='' multiple='multiple' size=10 onchange='populateSecondDropdown(this, 'http://yourprojectUrl','Any Subject');'>";
// printing the list box select command
echo "<option value=''>All</option>";
while($ntc=mysqli_fetch_array($queryc))
{//Array or records stored in $nt
echo "<option value="$ntc[course]">"$ntc[course]"</option>";
/* Option values are added by looping through the array */
}
echo "</select>";// Closing of list box
在populateSecondDropdown()函数内部定义一个ajax调用 -
Define an ajax call inside inside the populateSecondDropdown() function -
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
<script type="text/javascript">
function populateSecondDropdown(object,baseUrl)
{
$.ajax({
type: "POST",
url: baseUrl+"/ajax/fetchOptions.php",
data: { id_option: $(object).val(), operation: 'get_subjects' },
dataType: "json",
success: function(data)
{
//Clear options corresponding to earlier option of first dropdown
$('select#secondDropdown').empty();
$('select#secondDropdown').append('<option value="0">Select Option</option>');
//Populate options of the second dropdown
$.each( data.subjects, function()
{
$('select#secondDropdown').append('<option value="'+$(this).attr('option_id')+'">'+$(this).attr('option_name')+'</option>');
});
$('select#secondDropdown').focus();
},
beforeSend: function()
{
$('select#secondDropdown').empty();
$('select#secondDropdown').append('<option value="0">Loading...</option>');
},
error: function()
{
$('select#secondDropdown').attr('disabled', true);
$('select#secondDropdown').empty();
$('select#secondDropdown').append('<option value="0">No Options</option>');
}
});
}
</script>
最后是在 AJAX 处理器文件 fetchOptions.php 中获取第二个下拉选项的查询.您可以在此处使用 $_POST['id_option'] 来获取其下的选项.此处的数据库查询应获取每个选项的
option_id和option_name字段(正如$.each中的 jquery 代码所预期的那样)并返回一个json 编码的数组是这样的:-And finally the query to fetch 2nd dropdown's options in the AJAX processor file fetchOptions.php. You can use $_POST['id_option'] here to fetch the options under it. The database query here should fetch the
option_idandoption_namefields for every option (as expected by the jquery code inside$.each) and return a json encoded array like this:-return json_encode(array("subjects" => $resultOfQuery));获取按第一个下拉列表的字段分组的第二个下拉列表的所有数据.例如.让我们学习第一个下拉菜单中显示的课程和第二个显示的课程下的科目
Fetch all the data for the second dropdown grouped by the field of the first dropdown. E.g. let's take courses displayed in the first dropdown and subjects under courses displayed in the 2nd
创建第二个下拉列表的所有选项.在创建如下选项时分配与课程相同的课程:-
Create all the options of the 2nd dropdown. Assign classes equal to the courses while creating the options like this:-
第二种方法(仅使用 javascript)
$querycourse = "SELECT course, subject FROM subjects WHERE subject IS NOT NULL GROUP BY course "; $procc = mysqli_prepare($link, $querycourse); $queryc = mysqli_query($link, $querycourse) or die(mysqli_error($link)); echo "<select name='subjects[]' value='' multiple='multiple' size=100>"; echo "<option value=''>All</option>"; while($ntc=mysqli_fetch_array($queryc)) {//Array or records stored in $nt echo "<option value="$ntc[subject]" class="$ntc[course]">"$ntc[subject]"</option>"; } echo "</select>";然后为第一个下拉列表定义
onchange="displaySubjectsUnderThisCourse(this);"并编写此 javascript :-Then define
onchange="displaySubjectsUnderThisCourse(this);"for the first dropdown and write this javascript :-function displaySubjectsUnderThisCourse(object) { var selectedCourse = $(object).val(); //Display the options with class = the selected option from first dropdown $("."+selectedCourse).removeClass("hidden"); //define a class hidden with display:none; $('option:not(.selectedCourse)').hide(); // hide all options whose class is other than selectedCourse - Not sure whether this will work or not, though //Deselect any previous selections //If single option selection is allowed $('select#secondDropdown option').attr('selected', false); // or following if multiple selection is allowed (needed for IE) $('select#secondDropdown option').attr('selectedIndex', -1); }这里的基本思想是隐藏/显示选项组，但我的代码可能有错误.
The basic idea here is to hide/display option groups but my code may have errors.
最后，请注意，第二种方法(获取所有选项值)只有在您的数据量有限并且非常确定将来数据量总是会减少的情况下才会更好.但是，由于没有人能够对未来如此确定，因此建议始终使用 AJAX 方法.
Finally, please note, the second method (fetching all the option values) would be better only if you have limited small amount of data and are very sure there will always be less data in future. But, since nobody can be so certain about the future, it is advisable to use the AJAX method always.
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