php - 如何查询 html 选择表单？

Question

这是我的 html 选择表单。

<select name='md' multiple="yes" size="10">
                <optgroup label="Оpel">
                    <option value="Astra" name='Ast'>Astra</option>
                                </optgroup>
                                <optgroup label="Nissan">        
                    <option value="Pulsar" name='Puls'>Pulsar</option>
                    <option value="Almera" name='Alm'>Almera</option>
                </optgroup>
                <optgroup label="Honda">
                    <option value="Civic" name='Civ'>Civic</option>
                                 </optgroup>     
                                 <optgroup label="Audi">
                    <option value="Q7" name='Q'>Q7</option>                 
                </optgroup>

                <optgroup label="BMW">
                    <option value="M3" name='M'>M3</option>
                    </optgroup>
                                <optgroup label="Renault">
                                        <option value="Megane" name='Meg'>Megane</option>
                    </optgroup>
                                <optgroup label="Mercedes">
                                        <option value="G-Class" name='G'>G-Class</option>
                                        </optgroup>
                        </select>

这是我的 PHP:

$md = (isset($_POST['md']));

我应该如何进行查询，以便当用户从选择菜单中选择一个选项时调用表中与所选选项匹配的所有行。

这是我的整个查询，我需要将选择字段添加为变量以供用户搜索。

 $sql = "
 SELECT c.brand
      , c.model
      , c.reg_num
      , c.horse_powers
      , c.color
      , u.first_name
      , u.last_name 
   FROM cars c
   JOIN clients_cars uc 
     ON c.id = uc.cars_id 
   JOIN clients u
     ON uc.clients_id = u.id 
  WHERE c.id IN (   SELECT DISTINCT clients_cars.cars_id 
                               FROM clients_cars 
                              WHERE rent_date BETWEEN '$d1' AND '$d2' 
                                 OR return_date BETWEEN '$d1' AND '$d2' 
                                 OR ((return_date>'$d2')AND(rent_date<'$d1')) 
                                 OR ((horse_powers > '$hp1') AND (horse_powers < '$hp2'))
                   )
  "; 

应该是这样还是我错了？

SELECT * FROM table1 WHERE column1 LIKE '%$md%';

Answer 1

你应该为这个实现使用ajax，

$('#id_of_select').change(function(){

    $value = $(this).val();
    $.post('new_php_file.php',{md:$value},function(response){
        alert(response);
    })

});

new_php_file.php :

<?php
    $md = $_POST['md'];
    //You can use it now as you wanted...like SELECT * FROM table1 WHERE column1 LIKE '%$md%'; Just dont forget to echo your result.      
?> 

::::::::::::::::::::::::::::::::::::::::::::::::编辑::::::::::::::::::::::::::::::::::::::::::::

没有 Ajax:

我假设你在 index.php 中工作

HTML:

<form method="POST"> <!-- No need to set action parameter -->
    <select name='md' multiple="yes" size="10">
    ..
    ..
    <input type="submit" value="Click to Submit"/>
</form>

PHP:

在同一个 index.php 文件中，

 <?php

      if(isset($_POST['md']))
      {
          $md = $_POST['md']; 

         // Your business logic here

      }
 ?>