Creating Meta-boxes - php

Question

Found a function which add to my admin panel one meta-box. It's looks nice, but not enough.
I need at least ten custom fields. How to create them?
The questoins looks stupid, because my knowledge of php are minimal, so do not judge strictly ;). I will be grateful for the solution of this problem or an explanation of how it should work.
function myplugin_add_meta_box() {
$screens = array( 'post', 'page' );
foreach ( $screens as $screen ) {
add_meta_box(
'myplugin_sectionid',
__( 'My Post Section Title', 'myplugin_textdomain' ),
'myplugin_meta_box_callback',
$screen
);
}
}
add_action( 'add_meta_boxes', 'myplugin_add_meta_box' );
/**
* Prints the box content.
*
* #param WP_Post $post The object for the current post/page.
*/
function myplugin_meta_box_callback( $post ) {
wp_nonce_field( 'myplugin_meta_box', 'myplugin_meta_box_nonce' );
$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.
*
* #param int $post_id The ID of the post being saved.
*/
function myplugin_save_meta_box_data( $post_id ) {
if ( ! isset( $_POST['myplugin_meta_box_nonce'] ) ) {
return;
}
if ( ! wp_verify_nonce( $_POST['myplugin_meta_box_nonce'], 'myplugin_meta_box' ) ) {
return;
}
if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
return;
}
if ( isset( $_POST['post_type'] ) && 'page' == $_POST['post_type'] ) {
if ( ! current_user_can( 'edit_page', $post_id ) ) {
return;
}
} else {
if ( ! current_user_can( 'edit_post', $post_id ) ) {
return;
}
}
if ( ! isset( $_POST['myplugin_new_field'] ) ) {
return;
}
$my_data = sanitize_text_field( $_POST['myplugin_new_field'] );
update_post_meta( $post_id, '_my_meta_value_key', $my_data );
}
add_action( 'save_post', 'myplugin_save_meta_box_data' );

Answer 1

If your knowledge of PHP is quite low, there are some great plugins that allow you to do this easily.
If you have a lot of fields to add, I usually find it easier to use the following plugin as ordering fields and pulling them out in themes is a lot easier than doing it manually.
http://wordpress.org/plugins/advanced-custom-fields/