Announcement Custom Field (Meta Box) and Custom Post Type Example

announcement-demo.php

<?php
/*
Plugin Name: Announcement Demo Plugin
Description: Site specific code changes for example.com
*/
/* Start Adding Functions Below this Line */


// Register Custom Post Type
function custom_post_type() {

	$labels = array(
		'name'                => _x( 'Announcments', 'Announcements', 'text_domain' ),
		'singular_name'       => _x( 'Announcment', 'Announcment', 'text_domain' ),
		'menu_name'           => __( 'Announcments', 'text_domain' ),
		'name_admin_bar'      => __( 'Announcments', 'text_domain' ),
		'parent_item_colon'   => __( 'Parent Item:', 'text_domain' ),
		'all_items'           => __( 'All Items', 'text_domain' ),
		'add_new_item'        => __( 'Add New Item', 'text_domain' ),
		'add_new'             => __( 'Add New', 'text_domain' ),
		'new_item'            => __( 'New Item', 'text_domain' ),
		'edit_item'           => __( 'Edit Item', 'text_domain' ),
		'update_item'         => __( 'Update Item', 'text_domain' ),
		'view_item'           => __( 'View Item', 'text_domain' ),
		'search_items'        => __( 'Search Item', 'text_domain' ),
		'not_found'           => __( 'Not found', 'text_domain' ),
		'not_found_in_trash'  => __( 'Not found in Trash', 'text_domain' ),
	);
	$args = array(
		'label'               => __( 'announcments', 'text_domain' ),
		'description'         => __( 'Announcment', 'text_domain' ),
		'labels'              => $labels,
		'supports'            => array( ),
		'taxonomies'          => array( 'category', 'post_tag' ),
		'hierarchical'        => false,
		'public'              => true,
		'show_ui'             => true,
		'show_in_menu'        => true,
		'menu_position'       => 5,
		'show_in_admin_bar'   => true,
		'show_in_nav_menus'   => true,
		'can_export'          => true,
		'has_archive'         => true,		
		'exclude_from_search' => false,
		'publicly_queryable'  => true,
		'capability_type'     => 'post',
	);
	register_post_type( 'announcements', $args );

}

// Hook into the 'init' action
add_action( 'init', 'custom_post_type', 0 );




/**
 * Adds a box to the main column on the Custom Post Type Announcements edit screens.
 */
function announcement_add_meta_box() {

	$screens = array( 'announcements' );

	foreach ( $screens as $screen ) {

		add_meta_box(
			'announcement_sectionid',
			__( 'Announcement Dates', 'announcement_textdomain' ),
			'announcement_meta_box_callback',
			$screen
		);
	}
}
add_action( 'add_meta_boxes', 'announcement_add_meta_box' );

/**
 * Prints the box content.
 * 
 * @param WP_Post $post The object for the current post/page.
 */
function announcement_meta_box_callback( $post ) {

	// Add a nonce field so we can check for it later.
	wp_nonce_field( 'announcement_save_meta_box_data', 'announcement_meta_box_nonce' );

	/*
	 * 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="announcement_end_date">';
	_e( 'End Date:', 'announcement_textdomain' );
	echo '</label> ';
	echo '<input type="text" id="announcement_end_date" name="announcement_end_date" value="' . esc_attr( $value ) . '" size="25" /><br />';
}

/**
 * When the post is saved, saves our custom data.
 *
 * @param int $post_id The ID of the post being saved.
 */
function announcement_save_meta_box_data( $post_id ) {

	/*
	 * We need to verify this came from our screen and with proper authorization,
	 * because the save_post action can be triggered at other times.
	 */

	// Check if our nonce is set.
	if ( ! isset( $_POST['announcement_meta_box_nonce'] ) ) {
		return;
	}

	// Verify that the nonce is valid.
	if ( ! wp_verify_nonce( $_POST['announcement_meta_box_nonce'], 'announcement_save_meta_box_data' ) ) {
		return;
	}

	// If this is an autosave, our form has not been submitted, so we don't want to do anything.
	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
		return;
	}

	// Check the user's permissions.
	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;
		}
	}

	/* OK, it's safe for us to save the data now. */
	
	// Make sure that it is set.
	if ( ! isset( $_POST['announcement_end_date'] ) ) {
		return;
	}

	// Sanitize user input.
	$my_data = sanitize_text_field( $_POST['announcement_end_date'] );

	// Update the meta field in the database.
	update_post_meta( $post_id, '_my_meta_value_key', $my_data );
}
add_action( 'save_post', 'announcement_save_meta_box_data' );

/* Stop Adding Functions Below this Line */
?>