php - 如何使用sql在php的选择框中显示先前选择的选择选项

Question

<tr>
  <td>Select location</td>
  <td>
    <select name="contractors" id="contractors" class="autofill" style="width:100%" onchange="fetch_con1(this.value);">
        <option value="all" selected='selected'>All contractors</option>

        <?php $location->location_options(); ?> 
    </select>   
  </td>
</tr>

以上是我的代码的一部分。当我选择位置时，如果我在刷新页面后单击提交按钮，它不会显示以前输入的位置。我通过调用 function(<?php $location->location_options(); ?>) 显示数据库中的位置。 .这是我的位置功能:

function location_options() {       
    global $db;     
    $query = 'SELECT * from locations ORDER by location_name ASC';      
    $result = $db->query($query) or die($db->error);        
    $options = '';  

    if ($location_id!= '') {            
        while($row = $result->fetch_array()) {              
            if ($location_id == $row['location_id']) {              
                $options .= '<option selected="selected" value="'.$row['location_id'].'">'.$row['location_name'].'</option>';               
            } else  {               
               $options .= '<option value="'.$row['location_id'].'">'.$row['location_name'].'</option>';                
            }           
        }       
    } else {            
       while ($row = $result->fetch_array()) {              
           $options .= '<option value="'.$row['location_id'].'">'.$row['location_name'].'</option>';            
       }        
    }       
       echo $options;       
    }

这是我的定位功能

Answer 1

如果 $location_id 是在函数之外定义的，那么这可能会按预期工作，尽管正如在之前的评论中指出的那样 - 您还应该删除 selected='selected' 来自硬编码选项“所有承包商”

function location_options() {       
    global $db;
    global $location_id;
    /* Assume that the javascript function sends a post / get request with location_id as a parameter */
    if( isset( $_REQUEST['location_id'] ) ) $location_id=$_REQUEST['location_id'];

    $query = 'SELECT * from locations ORDER by location_name ASC';      
    $result = $db->query($query) or die($db->error);        
    $options = '';  

    if( isset( $location_id ) && $location_id!= '' ) {            
        while( $row = $result->fetch_array() ) {   
            $selected=( $location_id == $row['location_id'] ) ? " selected='selected'" : "";
            $options.='<option '.$selected.' value="'.$row['location_id'].'">'.$row['location_name'];
        }
    } else {            
       while( $row = $result->fetch_array() ) {
           $options .= '<option value="'.$row['location_id'].'">'.$row['location_name'];            
       }        
    }       
    echo $options;       
}