如何从PHP下拉列表中获取选定值的值？

嗨，在PHP中，我们可以使用Submit按钮或javascript提交表单。如果您只想使用php，则应添加一个提交按钮并检查是否已发布，然后检查此类。

        <form name="form" method="POST" style="display:inline;">
                    <select name="category" id="category" value="category" class="form-control ddplaceholder" style="width:220px;font-size:18px;font-family:Roboto;">
                         <option value="" disabled selected>Select Category</option>
                    <?php
                    $sth = $conn->prepare('Select name From category');
                    $sth->execute();
                    $data = $sth->fetchAll();   
                    foreach ($data as $row ){
                        if($row['name']!="")
                     echo ' <option id=\"CategoryName\" nameCategoryNameVendorName\" value="' .$row['name']. '">'.$row['name'].'</option>';
                    }
                    ?> 
                    </select>
    <input type="submit" name="submit" value="submit">
             </form>

<?php

    if(isset($_POST['submit'])){
         $category=$_POST['category'];}


or you can try javascript for  submission it will work on change of value in select box

    <form name="form" method="POST" style="display:inline;">
                <select name="category" id="category" value="category" class="form-control ddplaceholder" style="width:220px;font-size:18px;font-family:Roboto;" onchange="document.form.submit();">
                     <option value="" disabled selected>Select Category</option>
                <?php
                $sth = $conn->prepare('Select name From category');
                $sth->execute();
                $data = $sth->fetchAll();   
                foreach ($data as $row ){
                    if($row['name']!="")
                 echo ' <option id=\"CategoryName\" nameCategoryNameVendorName\" value="' .$row['name']. '">'.$row['name'].'</option>';
                }
                ?> 
                </select>
         </form>

<?php 

if(!empty($_POST['category']))
     $category=$_POST['category'];