php 为 HTML 表单下拉列表指定默认选定项
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Specify a default selected item for HTML form drop-downs
提问by TheFlash
Typically when you need to select an item by default, you do:
通常，当您需要默认选择一个项目时，您会执行以下操作：
<select>
<option value="1"> Volvo </option>
<option value="2" selected="true"> Saab </option>
<option value="3"> Mercedes </option>
<option value="4"> Audi </option>
</select>
Is it possible to get something like this?
有可能得到这样的东西吗？
<select selectedValue="2">
<option value="1"> Volvo </option>
<option value="2"> Saab </option>
<option value="3"> Mercedes </option>
<option value="4"> Audi </option>
</select>
It works out easier in PHP since you only have to soft-code one value, instead of handling the selected attribute on any possible <option/>.
在 PHP 中使用起来更容易，因为您只需对一个值进行软编码，而不用在任何可能的<option/>.
采纳答案by dmitko
Put JavaScript after the declaration of the listbox and set the selected index there:
将 JavaScript 放在列表框的声明之后，并在那里设置选定的索引：
<script>
document.getElementById('listBoxId').selectedIndex=<?php echo $INDEX ?>;
</script>
Something like this.
像这样的东西。
回答by roryf
There is no attribute like that on the <select>element. Assuming your <option>output is in a loop, I don't see how it makes a huge difference:
<select>元素上没有这样的属性。假设您的<option>输出处于循环中，我看不出它是如何产生巨大差异的：
$selected = "2";
foreach($values as $key => $val) {
echo "<option value=\"" . $key . "\"" . ($key == $selected ? " selected=\"selected\">" : ">") . $val . "</option>";
}
(my PHP is a little rusty, that may not be 100% correct)
（我的 PHP 有点生疏，可能不是 100% 正确）
回答by corroded
No, but you can add your default value to your id like
不，但您可以将默认值添加到您的 id 中，例如
<select id="default-value-2">
then in your options, you have
然后在你的选择中，你有
<option value="2" <?php echo is_this_the_default_value ? selected='true' : '' ?>
or something to that effect(forgive me i forgot my php syntax, but i hope you get the point).
或类似的东西（请原谅我忘记了我的 php 语法，但我希望你明白这一点）。
Anyway, that is a dirty fix also, so i suggest just adding a method to check for the default selected tag and printing it selected="selected" when it is the default. You can just call it once if you loop through your select options
无论如何，这也是一个肮脏的修复，所以我建议只添加一个方法来检查默认选择的标签，并在默认时打印它 selected="selected" 。如果您循环选择选项，您可以只调用一次
回答by Serendipity
You can do it like this:
你可以这样做：
$value = 1;
<select>
<?php if($value==1) echo "<option selected='true'> Volvo </option>";
else echo "<option> Volvo </option>"; ?>
<?php if($value==2) echo "<option selected='true'> Saab </option>";
else echo "<option> Saab </option>"; ?>
</select>
回答by acSlater
I found myself googling this to see if there was a better way to do it.
我发现自己在谷歌上搜索这个，看看是否有更好的方法来做到这一点。
The best and cleanest answer is from @roryf, however if you are not looping through your data I thought it would be a lot cleaner to wrap it up in a function:
最好和最干净的答案来自@roryf，但是如果你不循环遍历你的数据，我认为将它包装在一个函数中会更清晰：
function set_selected($desired_value, $new_value)
{
if($desired_value==$new_value)
{
echo ' selected="selected"';
}
}
Then you would use it like this:
然后你会像这样使用它：
<?php $selected_value = 2; ?>
<select>
<option value="1"<?php set_selected('1', $selected_value); ?>> Volvo </option>
<option value="2"<?php set_selected('2', $selected_value); ?>> Saab </option>
<option value="3"<?php set_selected('3', $selected_value); ?>> Mercedes </option>
<option value="4"<?php set_selected('4', $selected_value); ?>> Audi </option>
</select>
This would set Saab as selected :)
这会将 Saab 设置为选中 :)
