数据库 <select> 标记的多项选择

Question

我想选择多个成员分配给一个组！ 目前，我可以选择一个成员，我可以将他分配到一个组中。 我想选择几个成员并将他们分配到一个组。

    <?php
        include 'connection.php';
        if( isset( $_POST['add_member'] ) )
        {
             $member_id = $_POST['member_id'];
             $group_id = $_POST['group_id'];

             $query="SELECT `id` FROM `member_group`
                        WHERE `member_id` = $member_id AND `group_id` =  $group_id";
            if(!mysqli_num_rows(mysqli_query($connection,$query)))
            {
                $query="INSERT INTO `member_group`(member_id,group_id) VALUES( $member_id,$group_id)";
                mysqli_query($connection,$query) or die(mysqli_errno($connection));
                echo "<div class='alert alert-info'>Member Assigned. </div>";
            }
        }
        elseif( isset( $_POST['remove_member'] ) )
        {
             $member_id = $_POST['member_id'];
             $group_id = $_POST['group_id'];

             $query="DELETE FROM `member_group`
                    WHERE `member_id` = $member_id AND `group_id` =  $group_id";
             $rows = mysqli_query($connection,$query);
            if(!mysqli_affected_rows($connection))
            {
                echo "<div class='alert alert-info'>Member Already Deleted. </div>";
            }
            else
            {
                    echo "<div class='alert alert-info'>Member Deleted. </div>";
            }
        }

    ?>
    <form action="" method="POST">
        <label> Add Member to the group: </label>
            <select name="member_id" required="required" name="selectionField"  multiple="yes">
                <option value="">Select a Member</option>
                <?php
                    $member_query = mysqli_query($connection, "select id, member_name , fname , email , mobile from `member`");
                    while($member_data = mysqli_fetch_object($member_query) ){
                        echo "<option value='$member_data->id'>$member_data->member_name</option>";
                    }
                ?>
            </select>
            <input type="submit" name="add_member" value="Add" class="btn btn-info" />
            <input type="submit" name="remove_member" value="Remove" class="btn btn-info" />
            <select name="group_id" required="required" name="selectionField" multiple="yes">
                <option value="">Select a Group</option>
                <?php
                    $group_query = mysqli_query($connection, "select id, name from `group`");
                    while($group_data = mysqli_fetch_object($group_query) ){
                        echo "<option value='$group_data->id'>$group_data->name</option>";
                    }
                ?>
            </select>
        <br />
    </form>

Answer 1

使用multiple attribute 选择复选框或复选框数组。

$members_id = is_array($_POST['add_member'])
            ? $_POST['add_member']
            : array($_POST['add_member'];

$check_query = "SELECT `id` FROM `member_group` WHERE `member_id` IN(".implode(',', $members_id).") AND `group_id` =  $group_id";

$already_added = array();
while($member = mysqli_fetch_object($check_query) ){
    $already_added[] = $member->id
}

$members_id = array_diff($members_id, $already_added);

if(count($members_id) > 0) {

    // Add members to DB
    $query = 'INSERT INTO `member_group`(member_id,group_id) VALUES';

    foreach($remove_member as $member_id) {
        $query .= " ($member_id, $group_id)";
    }
    $member_query = mysqli_query($query);
}

第一个查询获取已经添加的用户，然后将这些用户的数组与 $members_id 进行比较。添加不在数据库中的那些（第二个查询）。

顺便说一句，如果您不保护您的代码免受 SQL injection 的侵害。即使用mysqli_real_escape_string。

Answer 2

代替：

<select name="member_id" required="required" name="selectionField" multiple="yes">

做：

<select required="required" name="selectionField[]" multiple="yes">

这样你就告诉 PHP 选择是一个数组，其位置与用户选择的元素一样多。

获取数组中的信息：

$member_id = $_POST['selectionField'];

for ($i=0;$i<count($member_id);$i++)
{
   $currentMember = $member_id[$i];
// Your code to insert the member in the DB
}