我认为这可能是我的PHP的问题，而不是我使用设置API的问题，但我似乎无法让Wordpress为多选框保存数据数组。

多选框对应一个自定义元字段，选择选项是显示该元字段的自定义帖子类型。

以下是显示代码：

case \'select2\':  
        echo "<select id=\'$id\' style=\'width:15em;height:10em;\' class=\'select$field_class\' name=\'" . $buddha_option_name . "[$id]\' multiple>";  
        foreach($choices as $item) {  

            $item = explode("|",$item);  
            $item[0] = esc_html($item[0], \'buddha_textdomain\');  

            $selected = ($options[$id]==$item[1]) ? \'selected="selected"\' : \'\';  
            echo "<option value=\'$item[1]\' $selected>$item[0]</option>";  
        } 
        echo "</select>";  
        echo ($desc != \'\') ? "<br /><span class=\'description\'>$desc</span>" : ""; 
    break;  

$options[] = array(  
    "section" => "custom_meta",  
    "id"      => BUDDHA_SHORTNAME . "_meta_email",  
    "title"   => __( \'Email Meta Box\', \'buddha_textdomain\' ),  
    "desc"    => __( \'Select post types to have custom email meta box.\', \'buddha_textdomain\' ),  
    "type"    => "select2",  
    "std"    => print_r($buddha_option_name[$id]),  
    "choices" => array( __(\'Posts\',\'buddha_textdomain\') . "|post", __(\'Pages\',\'buddha_textdomain\') . "|page", __(\'Faculty/Staff\',\'buddha_textdomain\') . "|staff", __(\'FAQ\',\'buddha_textdomain\') . "|faq", __(\'Documents\',\'buddha_textdomain\') . "|docs", __(\'Courses\',\'buddha_textdomain\') . "|courses" )  
);

case \'select2\': 
                // process $select_values 
                    $select_values = array(); 
                    foreach ($option[\'choices\'] as $k => $v) { 
                        // explode the connective 
                        $pieces = explode("|", $v); 

                        $select_values[] = $pieces[1]; 
                    } 
                // check to see if selected value is in our approved array of values! 
                $valid_input[$option[\'id\']] = (in_array( $input[$option[\'id\']], $select_values) ? $input[$option[\'id\']] : \'\' ); 
            break; 

我想添加[] 至年底[$id] 可能会有帮助，但不会。