update_post_meta()

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概述

update_post_meta() 函数用于更新指定文章 ID 的元数据字段，若字段不存在则自动添加。它支持通过 $prev_value 参数区分相同键名的多个值，并处理转义和序列化数据。

关键要点

函数基于文章 ID 更新元数据，可替代 add_post_meta() 使用
参数包括 $post_id（必填）、$meta_key（必填）、$meta_value（必填，非标量需可序列化）和 $prev_value（可选，用于指定更新条件）
返回值：元数据不存在时返回 Meta ID，成功更新返回 true，失败或值未变返回 false
历史原因要求输入时元键和元值需“转义”（使用 wp_slash 补偿 stripslashes() 调用）
注意处理 JSON 等包含转义字符的数据，避免存储转义值

代码示例

// 更新页面模板示例
update_post_meta( $page_id, '_wp_page_template', 'new_template.php' );

注意事项

当 $meta_value 与数据库现有值相同时，函数返回 false
若未设置 $prev_value，同一键名的所有值都会被更新
处理序列化数据时需注意数组结构，避免嵌套问题
数据库排序规则为大小写不敏感时，update_post_meta() 可能影响大小写不同的键，但 get_post_meta() 因缓存保持敏感

📄 原文内容

Updates a post meta field based on the given post ID.

Description

Use the $prev_value parameter to differentiate between meta fields with the same key and post ID.

If the meta field for the post does not exist, it will be added and its ID returned.

Can be used in place of add_post_meta() .

For historical reasons both the meta key and the meta value are expected to be “slashed” (slashes escaped) on input.

Parameters

$post_idintrequired: Post ID.
$meta_keystringrequired: Metadata key.
$meta_valuemixedrequired: Metadata value. Must be serializable if non-scalar.
$prev_valuemixedoptional: Previous value to check before updating.
If specified, only update existing metadata entries with this value. Otherwise, update all entries. Default empty.

Return

int|bool Meta ID if the key didn’t exist, true on successful update, false on failure or if the value passed to the function is the same as the one that is already in the database.

More Information

Character Escaping

Post meta values are passed through the stripslashes() function upon being stored, so you will need to be careful when passing in values (such as JSON) that might include escaped characters.

Do not store escaped values

Consider the JSON value {"key":"value with "escaped quotes""}

Workaround

By adding one more level of escaping using function wp_slash (introduced in WP 3.6), you can compensate for the call to stripslashes()

Source

function update_post_meta( $post_id, $meta_key, $meta_value, $prev_value = '' ) {
	// Make sure meta is updated for the post, not for a revision.
	$the_post = wp_is_post_revision( $post_id );
	if ( $the_post ) {
		$post_id = $the_post;
	}

	return update_metadata( 'post', $post_id, $meta_key, $meta_value, $prev_value );
}

View all references View on Trac View on GitHub

Uses	Description
wp_is_post_revision()`wp-includes/revision.php`	Determines if the specified post is a revision.
update_metadata()`wp-includes/meta.php`	Updates metadata for the specified object. If no value already exists for the specified object ID and metadata key, the metadata will be added.

Used by	Description
WP_REST_Attachments_Controller::edit_media_item()`wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php`	Applies edits to a media item and creates a new attachment record.
_wp_privacy_account_request_confirmed()`wp-includes/user.php`	Updates log when privacy request is confirmed.
_wp_privacy_send_request_confirmation_notification()`wp-includes/user.php`	Notifies the site administrator via email when a request is confirmed.
_wp_privacy_send_erasure_fulfillment_notification()`wp-includes/user.php`	Notifies the user when their erasure request is fulfilled.
wp_privacy_process_personal_data_export_page()`wp-admin/includes/privacy-tools.php`	Intercept personal data exporter page Ajax responses in order to assemble the personal data export file.
wp_privacy_generate_personal_data_export_file()`wp-admin/includes/privacy-tools.php`	Generate the personal data export file.
_wp_privacy_completed_request()`wp-admin/includes/privacy-tools.php`	Marks a request as completed by the admin and logs the current timestamp.
WP_Customize_Manager::set_changeset_lock()`wp-includes/class-wp-customize-manager.php`	Marks the changeset post as being currently edited by the current user.
WP_Customize_Manager::refresh_changeset_lock()`wp-includes/class-wp-customize-manager.php`	Refreshes changeset lock with the current time if current user edited the changeset before.
WP_Customize_Manager::dismiss_user_auto_draft_changesets()`wp-includes/class-wp-customize-manager.php`	Dismisses all of the current user’s auto-drafts (other than the present one).
WP_Customize_Manager::import_theme_starter_content()`wp-includes/class-wp-customize-manager.php`	Imports theme starter content into the customized state.
WP_REST_Attachments_Controller::create_item()`wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php`	Creates a single attachment.
WP_REST_Attachments_Controller::update_item()`wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php`	Updates a single attachment.
WP_REST_Posts_Controller::handle_template()`wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php`	Sets the template for a post.
Custom_Background::ajax_background_add()`wp-admin/includes/class-custom-background.php`	Handles Ajax request for adding custom background context to an attachment.
wp_restore_image()`wp-admin/includes/image-edit.php`	Restores the metadata for a given attachment.
wp_save_image()`wp-admin/includes/image-edit.php`	Saves image to post, along with enqueued changes in `$_REQUEST['history']`.
wp_generate_attachment_metadata()`wp-admin/includes/image.php`	Generates attachment meta data and create image sub-sizes for images.
media_upload_form_handler()`wp-admin/includes/media.php`	Handles form submissions for the legacy media uploader.
wp_set_post_lock()`wp-admin/includes/post.php`	Marks the post as currently being edited by the current user.
edit_post()`wp-admin/includes/post.php`	Updates an existing post with values provided in `$_POST`.
bulk_edit_posts()`wp-admin/includes/post.php`	Processes the post data for the bulk editing of posts.
wp_ajax_upload_attachment()`wp-admin/includes/ajax-actions.php`	Handles uploading attachments via AJAX.
wp_ajax_wp_remove_post_lock()`wp-admin/includes/ajax-actions.php`	Handles removing a post lock via AJAX.
wp_ajax_save_attachment()`wp-admin/includes/ajax-actions.php`	Handles updating attachment attributes via AJAX.
Custom_Image_Header::ajax_header_add()`wp-admin/includes/class-custom-image-header.php`	Given an attachment ID for a header image, updates its “last used” timestamp to now.
Custom_Image_Header::customize_set_last_used()`wp-admin/includes/class-custom-image-header.php`	Updates the last-used postmeta on a header image attachment after saving a new header image via the Customizer.
Custom_Image_Header::set_header_image()`wp-admin/includes/class-custom-image-header.php`	Chooses a header image, selected from existing uploaded and default headers, or provides an array of uploaded header data (either new, or from media library).
Custom_Background::wp_set_background_image()`wp-admin/includes/class-custom-background.php`
Custom_Background::handle_upload()`wp-admin/includes/class-custom-background.php`	Handles an Image upload for the background image.
WP_Embed::shortcode()`wp-includes/class-wp-embed.php`	The do_shortcode() callback function.
set_post_thumbnail()`wp-includes/post.php`	Sets the post thumbnail (featured image) for the given post.
wp_update_attachment_metadata()`wp-includes/post.php`	Updates metadata for an attachment.
wp_insert_post()`wp-includes/post.php`	Inserts or update a post.
update_attached_file()`wp-includes/post.php`	Updates attachment file path based on attachment ID.
wp_restore_post_revision()`wp-includes/revision.php`	Restores a post to the specified revision.
wp_update_nav_menu_item()`wp-includes/nav-menu.php`	Saves the properties of a menu item or create a new one.

Show 32 more Show less

Changelog

Version	Description
1.5.0	Introduced.

User Contributed Notes

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lucerny

7 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 6You must log in to vote on the helpfulness of this note

Note that this function will also return false when $meta_value is equal to the value you try to update in database.

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Aurovrata Venet

8 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 4You must log in to vote on the helpfulness of this note
Update the template used by a page,
```
update_post_meta( $page_id, '_wp_page_template', 'new_template.php' );
```
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Fiaz Husyn

11 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note

Note: if there are multiple values for a single key, all the values will get updated if $prev_value is not set.

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elmachoiq

5 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note
¡IMPORTANT If you are working with serialized data, the array is updated with an extra nested array
In order to keep the same structure, update the Object in the 1rst nested position.
```
$ticket_meta = get_post_meta($azgTorneoID,"mep_event_ticket_type",)
$ticket_meta[0][0]["option_rsv_t"] = "9";
update_post_meta($azgTorneoID,"mep_event_ticket_type",$ticket_meta[0]);
```
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Codex

11 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
Other Examples
Assuming a post has an ID of 76, and the following 4 custom fields:

[key_1] => 'Happy'
[key_1] => 'Sad'
[key_2] => 'Gregory'
[my_key] => 'Steve'

To change key_2’s value to Hans:
To change key_1’s value from Sad to Happy:
The fields would now look like this:

[key_1] => 'Happy'
[key_1] => 'Happy'
[key_2] => 'Hans'
[my_key] => 'Steve'

Note: This function will update only the first field that matches the criteria.

To change the first key_1’s value from Happy to Excited:
Edit Page template

[/php]

For a more detailed example, go to the post_meta Functions Examples page.
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Drew Jaynes

7 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: -1You must log in to vote on the helpfulness of this note

Please note that if your database collation is case insensitive (as with suffix _ci) then update_post_meta() and delete_post_meta() and get_posts() will update/delete/query the meta records with keys that are upper or lower case. However get_post_meta() will be case sensitive due to WordPress caching. See https://core.trac.wordpress.org/ticket/18210 for more info.

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Codex

11 years ago

You must log in to vote on the helpfulness of this noteVote results for this note: -2You must log in to vote on the helpfulness of this note
Default Usage
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