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The add_meta_box() function was introduced in Version 2.5. It allows plugin developers to add meta boxes to the administrative interface.
<?php
add_meta_box( $id, $title, $callback, $post_type, $context,
$priority, $callback_args );
?>
None.
Here is an example that adds a custom section to the post and page editing screens:
<?php
/* Define the custom box */
add_action( 'add_meta_boxes', 'myplugin_add_custom_box' );
// backwards compatible (before WP 3.0)
// add_action( 'admin_init', 'myplugin_add_custom_box', 1 );
/* Do something with the data entered */
add_action( 'save_post', 'myplugin_save_postdata' );
/* Adds a box to the main column on the Post and Page edit screens */
function myplugin_add_custom_box() {
$screens = array( 'post', 'page' );
foreach ($screens as $screen) {
add_meta_box(
'myplugin_sectionid',
__( 'My Post Section Title', 'myplugin_textdomain' ),
'myplugin_inner_custom_box',
$screen
);
}
}
/* Prints the box content */
function myplugin_inner_custom_box( $post ) {
// Use nonce for verification
wp_nonce_field( plugin_basename( __FILE__ ), 'myplugin_noncename' );
// The actual fields for data entry
// Use get_post_meta to retrieve an existing value from the database and use the value for the form
$value = get_post_meta( $post->ID, '_my_meta_value_key', true );
echo '<label for="myplugin_new_field">';
_e("Description for this field", 'myplugin_textdomain' );
echo '</label> ';
echo '<input type="text" id="myplugin_new_field" name="myplugin_new_field" value="'.esc_attr($value).'" size="25" />';
}
/* When the post is saved, saves our custom data */
function myplugin_save_postdata( $post_id ) {
// First we need to check if the current user is authorised to do this action.
if ( 'page' == $_POST['post_type'] ) {
if ( ! current_user_can( 'edit_page', $post_id ) )
return;
} else {
if ( ! current_user_can( 'edit_post', $post_id ) )
return;
}
// Secondly we need to check if the user intended to change this value.
if ( ! isset( $_POST['myplugin_noncename'] ) || ! wp_verify_nonce( $_POST['myplugin_noncename'], plugin_basename( __FILE__ ) ) )
return;
// Thirdly we can save the value to the database
//if saving in a custom table, get post_ID
$post_ID = $_POST['post_ID'];
//sanitize user input
$mydata = sanitize_text_field( $_POST['myplugin_new_field'] );
// Do something with $mydata
// either using
add_post_meta($post_ID, '_my_meta_value_key', $mydata, true) or
update_post_meta($post_ID, '_my_meta_value_key', $mydata);
// or a custom table (see Further Reading section below)
}
?>
This is an example of how to add a meta box from inside a class
/**
* Calls the class on the post edit screen
*/
function call_someClass()
{
return new someClass();
}
if ( is_admin() )
add_action( 'load-post.php', 'call_someClass' );
/**
* The Class
*/
class someClass {
const LANG = 'some_textdomain';
public function __construct() {
add_action( 'add_meta_boxes', array( $this, 'add_meta_box' ) );
add_action( 'save_post', array( $this, 'save' ) );
}
/**
* Adds the meta box container
*/
public function add_meta_box() {
add_meta_box(
'some_meta_box_name'
,__( 'Some Meta Box Headline', self::LANG )
,array( &$this, 'render_meta_box_content' )
,'post'
,'advanced'
,'high'
);
}
public function save( $post_id ) {
// First we need to check if the current user is authorised to do this action.
if ( 'page' == $_POST['post_type'] ) {
if ( ! current_user_can( 'edit_page', $post_id ) )
return;
} else {
if ( ! current_user_can( 'edit_post', $post_id ) )
return;
}
// Secondly we need to check if the user intended to change this value.
if ( ! isset( $_POST['myplugin_noncename'] ) || ! wp_verify_nonce( $_POST['myplugin_noncename'], plugin_basename( __FILE__ ) ) )
return;
// Thirdly we can save the value to the database
//if saving in a custom table, get post_ID
$post_ID = $_POST['post_ID'];
//sanitize user input
$mydata = sanitize_text_field( $_POST['myplugin_new_field'] );
// Do something with $mydata
// either using
if ( !add_post_meta( $post_ID, '_my_meta_value_key', $mydata, true ) ) {
update_post_meta( $post_ID, '_my_meta_value_key', $mydata );
}
// or a custom table (see Further Reading section below)
}
/**
* Render Meta Box content
*/
public function render_meta_box_content( $post ) {
// Use nonce for verification
wp_nonce_field( plugin_basename( __FILE__ ), 'myplugin_noncename' );
// The actual fields for data entry
// Use get_post_meta to retrieve an existing value from the database and use the value for the form
$value = get_post_meta( $post->ID, '_my_meta_value_key', true );
echo '<label for="myplugin_new_field">';
_e( 'Description for this field', 'myplugin_textdomain' );
echo '</label> ';
echo '<input type="text" id="myplugin_new_field" name="myplugin_new_field" value="'.esc_attr( $value ).'" size="25" />';
}
}
The $callback_args array will be passed to the callback function as the second argument. The first argument is the post's $post object.
// This function adds a meta box with a callback function of my_metabox_callback()
function add_my_meta_box() {
$var1 = 'this';
$var2 = 'that';
add_meta_box(
'metabox_id',
'Metabox Title',
'my_metabox_callback',
'page',
'normal',
'low',
array( 'foo' => $var1, 'bar' => $var2)
);
}
// $post is an object containing the current post (as a $post object)
// $metabox is an array with metabox id, title, callback, and args elements.
// The args element is an array containing your passed $callback_args variables.
function my_metabox_callback ( $post, $metabox ) {
echo 'Last Modified: '.$post->post_modified; // outputs last time the post was modified
echo $metabox['args']['foo']; // outputs 'this'
echo $metabox['args']['bar']; // outputs 'that'
echo get_post_meta($post->ID,'my_custom_field',true); // outputs value of custom field
}
add_meta_box() is located in wp-admin/includes/template.php.
