I found the code myself. I.e., here is the code of one custom field:
// ACTION TO ADD THE META BOX WE ARE DEFINING
add_action( 'add_meta_boxes_post', "name_add_meta_box" );
/*
* Routine to add a meta box. Called via a filter hook once WordPress is initialized
*/
function name_add_meta_box(){
add_meta_box(
"name_meta_box", // An ID for the Meta Box. Make it unique to your plugin
__( "Nome", 'textdomain' ), // The title for your Meta Box
"name_meta_box_render", // A callback function to fill the Meta Box with the desired UI in the editor
"post", // The screen name - in this case the name of our custom post type
"side" // The context or placement for the meta box. Choose "normal", "side" or "advanced"
);
}
/*
* Routine to display a custom meta box editor
* Note: In this example our custom meta data is saved as a row in the postmeta database table.
* $post PostObject An object representing a WordPress post that is currently being loaded in the post editor.
*/
function name_meta_box_render( $post ){
// Get the name and display it in a text field
$name = get_post_meta( $post->ID, "function_name", true );
echo '<div><input type="text" name="function_name" value="'.$name.'" placeholder="Nome" /></div>';
}
// Hook into the save routine for posts
add_action( 'save_post', 'name_meta_box_save');
/*
* Routine to save the custom post meta data from the editor
* Note: We retrieve the form data through the PHP Global $_POST
* $post_id int The ID of the post being saved
*/
function name_meta_box_save( $post_id ){
// Check to see if this is our custom post type (remove this check if applying the meta box globally)
if($_POST['post_type'] == "post"){
// Retrieve the values from the form
$name = $_POST['function_name'];
// Clean, sanitize and validate the input as appropriate
// Save the updated data into the custom post meta database table
update_post_meta( $post_id, "function_name", $name );
}
}
