问题描述
我在 WordPress 管理员的”Pages” 中添加了一个新页面，并添加了几个自定义字段。我也希望能够将一个上传图像字段添加到页面编辑器 – 有没有办法通过 custom-fields？
或者如果我需要这个能力，还有不同的方向吗？
最佳解决方案
对于任何想要了解更多文件上传的人来说，这里是一个简要的介绍主要话题和痛点的介绍。这是在 Linux 盒子上写的 WordPress 3.0，代码只是教授概念的基本概述。我相信这里的一些人可以提供改进实施的建议。
概述您的基本方法
将图像与帖子相关联至少有三种方法：使用 post_meta 字段存储图像路径，使用 post_meta 字段来存储图像的媒体库 ID(稍后再更新)，或将图像分配给帖子作为附件。此示例将使用 post_meta 字段来存储图像的媒体库 ID 。 YMMV 。
多部分编码
默认情况下，WordPress 创建& 编辑表单没有 enctype 。如果要上传文件，则需要将”enctype=’multipart/form-data'” 添加到表单标签中，否则 $ _FILES 集合将不会被推送。在 WordPress 3.0 中，有一个钩子。在某些以前的版本 (不确定具体细节) 中，您必须将字符串替换为表单标签。
function xxxx_add_edit_form_multipart_encoding() {
echo ' enctype="multipart/form-data"';
}
add_action('post_edit_form_tag', 'xxxx_add_edit_form_multipart_encoding');
创建元框和上传字段
我不会去创建元框，因为大多数人可能已经知道如何做，但我只想说，你只需要一个简单的元框，其中包含一个文件字段。在下面的示例中，我已经添加了一些代码来查找现有的图像，如果存在，则显示它。我还包括一些简单的错误/反馈功能，可以使用 post_meta 字段传递错误。你会想改变它来使用 WP_Error 类… 它只是为了演示。
function xxxx_render_image_attachment_box($post) {
// See if there's an existing image. (We're associating images with posts by saving the image's 'attachment id' as a post meta value)
// Incidentally, this is also how you'd find any uploaded files for display on the frontend.
$existing_image_id = get_post_meta($post->ID,'_xxxx_attached_image', true);
if(is_numeric($existing_image_id)) {
echo '<div>';
$arr_existing_image = wp_get_attachment_image_src($existing_image_id, 'large');
$existing_image_url = $arr_existing_image[0];
echo '<img src="'%20.%20$existing_image_url%20.%20'" />';
echo '</div>';
}
// If there is an existing image, show it
if($existing_image_id) {
echo '<div>Attached Image ID: ' . $existing_image_id . '</div>';
}
echo 'Upload an image: <input type="file" name="xxxx_image" id="xxxx_image" />';
// See if there's a status message to display (we're using this to show errors during the upload process, though we should probably be using the WP_error class)
$status_message = get_post_meta($post->ID,'_xxxx_attached_image_upload_feedback', true);
// Show an error message if there is one
if($status_message) {
echo '<div class="upload_status_message">';
echo $status_message;
echo '</div>';
}
// Put in a hidden flag. This helps differentiate between manual saves and auto-saves (in auto-saves, the file wouldn't be passed).
echo '<input type="hidden" name="xxxx_manual_save_flag" value="true" />';
}
function xxxx_setup_meta_boxes() {
// Add the box to a particular custom content type page
add_meta_box('xxxx_image_box', 'Upload Image', 'xxxx_render_image_attachment_box', 'post', 'normal', 'high');
}
add_action('admin_init','xxxx_setup_meta_boxes');
处理文件上传
这是大的 – 通过挂接到 save_post 操作来实际处理文件上传。我已经在下面添加了一个 heavily-commented 功能，但是我想注意它使用的两个关键的 WordPress 功能：
wp_handle_upload() 执行所有的魔术，好的，处理上传。你只需要在 $ _FILES 数组中传递一个对你的字段的引用，并且选择一个数组 (不要太担心这些 – 你需要设置的唯一重要的一个是 test_form = false 。但是，此功能不会将上传的文件添加到媒体库。它只是上传并返回新文件的路径 (并且，并且，方便地，完整的 URL) 。如果有问题，它会返回一个错误。
wp_insert_attachment() 将图像添加到媒体库，并生成所有适当的缩略图。您只需传递一系列选项 (标题，帖子状态等) 和 LOCAL 路径 (而不是 URL) 到您刚刚上传的文件。将图像放在媒体库中的好东西是，您可以稍后通过调用 wp_delete_attachment 并传递项目的媒体库 ID(我在下面的功能中) 来轻松删除所有文件。使用此功能，您还需要使用 wp_generate_attachment_metadata() 和 wp_update_attachment_metadata()，它们完全按照您期望的方式执行 – 为媒体项生成元数据。
function xxxx_update_post($post_id, $post) {
// Get the post type. Since this function will run for ALL post saves (no matter what post type), we need to know this.
// It's also important to note that the save_post action can runs multiple times on every post save, so you need to check and make sure the
// post type in the passed object isn't "revision"
$post_type = $post->post_type;
// Make sure our flag is in there, otherwise it's an autosave and we should bail.
if($post_id && isset($_POST['xxxx_manual_save_flag'])) {
// Logic to handle specific post types
switch($post_type) {
// If this is a post. You can change this case to reflect your custom post slug
case 'post':
// HANDLE THE FILE UPLOAD
// If the upload field has a file in it
if(isset($_FILES['xxxx_image']) && ($_FILES['xxxx_image']['size'] > 0)) {
// Get the type of the uploaded file. This is returned as "type/extension"
$arr_file_type = wp_check_filetype(basename($_FILES['xxxx_image']['name']));
$uploaded_file_type = $arr_file_type['type'];
// Set an array containing a list of acceptable formats
$allowed_file_types = array('image/jpg','image/jpeg','image/gif','image/png');
// If the uploaded file is the right format
if(in_array($uploaded_file_type, $allowed_file_types)) {
// Options array for the wp_handle_upload function. 'test_upload' => false
$upload_overrides = array( 'test_form' => false );
// Handle the upload using WP's wp_handle_upload function. Takes the posted file and an options array
$uploaded_file = wp_handle_upload($_FILES['xxxx_image'], $upload_overrides);
// If the wp_handle_upload call returned a local path for the image
if(isset($uploaded_file['file'])) {
// The wp_insert_attachment function needs the literal system path, which was passed back from wp_handle_upload
$file_name_and_location = $uploaded_file['file'];
// Generate a title for the image that'll be used in the media library
$file_title_for_media_library = 'your title here';
// Set up options array to add this file as an attachment
$attachment = array(
'post_mime_type' => $uploaded_file_type,
'post_title' => 'Uploaded image ' . addslashes($file_title_for_media_library),
'post_content' => '',
'post_status' => 'inherit'
);
// Run the wp_insert_attachment function. This adds the file to the media library and generates the thumbnails. If you wanted to attch this image to a post, you could pass the post id as a third param and it'd magically happen.
$attach_id = wp_insert_attachment( $attachment, $file_name_and_location );
require_once(ABSPATH . "wp-admin" . '/includes/image.php');
$attach_data = wp_generate_attachment_metadata( $attach_id, $file_name_and_location );
wp_update_attachment_metadata($attach_id, $attach_data);
// Before we update the post meta, trash any previously uploaded image for this post.
// You might not want this behavior, depending on how you're using the uploaded images.
$existing_uploaded_image = (int) get_post_meta($post_id,'_xxxx_attached_image', true);
if(is_numeric($existing_uploaded_image)) {
wp_delete_attachment($existing_uploaded_image);
}
// Now, update the post meta to associate the new image with the post
update_post_meta($post_id,'_xxxx_attached_image',$attach_id);
// Set the feedback flag to false, since the upload was successful
$upload_feedback = false;
} else { // wp_handle_upload returned some kind of error. the return does contain error details, so you can use it here if you want.
$upload_feedback = 'There was a problem with your upload.';
update_post_meta($post_id,'_xxxx_attached_image',$attach_id);
}
} else { // wrong file type
$upload_feedback = 'Please upload only image files (jpg, gif or png).';
update_post_meta($post_id,'_xxxx_attached_image',$attach_id);
}
} else { // No file was passed
$upload_feedback = false;
}
// Update the post meta with any feedback
update_post_meta($post_id,'_xxxx_attached_image_upload_feedback',$upload_feedback);
break;
default:
} // End switch
return;
} // End if manual save flag
return;
}
add_action('save_post','xxxx_update_post',1,2);
权限，所有权和安全性
如果您无法上传，可能与权限有关。我不是服务器配置的专家，所以请纠正我，如果这部分是愚蠢的。
首先，确保您的 wp-content / uploads 文件夹存在，并由 apache 拥有：apache 。如果是这样，您应该可以将权限设置为 744，并且所有内容都应该可以正常工作。所有权是重要的 – 即使设置为 777，如果目录没有正确拥有，有时也不会有帮助。
您还应考虑使用 htaccess 文件限制上传和执行的文件类型。这可以防止人们上传不是图像的文件，也不会执行伪装成图像的脚本。你应该可以 google 这个更权威的信息，但你可以这样做简单的文件类型限制：
<Files ^(*.jpeg|*.jpg|*.png|*.gif)>
order deny,allow
deny from all
</Files>
参考文献
注：本文内容整合自 Google/Baidu/Bing 辅助翻译的英文资料结果。如果您对结果不满意，可以加入我们改善翻译效果：薇晓朵技术论坛。