Meta Box

Author, Date,Category

class Custom_Meta_Box {

	public function __construct() {

		if ( is_admin() ) {
			add_action( 'load-post.php',     array( $this, 'init_metabox' ) );
			add_action( 'load-post-new.php', array( $this, 'init_metabox' ) );
		}

	}

	public function init_metabox() {

		add_action( 'add_meta_boxes',        array( $this, 'add_metabox' )         );
		add_action( 'save_post',             array( $this, 'save_metabox' ), 10, 2 );

	}

	public function add_metabox() {

		add_meta_box(
			'author',
			__( 'base', 'text_domain' ),
			array( $this, 'render_metabox' ),
			'post',
			'advanced',
			'default'
		);

	}

	public function render_metabox( $post ) {

		// Retrieve an existing value from the database.
		$custom_author name = get_post_meta( $post->ID, 'custom_author name', true );
		$custom_post_date = get_post_meta( $post->ID, 'custom_post_date', true );
		$custom_post_category = get_post_meta( $post->ID, 'custom_post_category', true );

		// Set default values.
		if( empty( $custom_author name ) ) $custom_author name = 'text';
		if( empty( $custom_post_date ) ) $custom_post_date = 'Date Saved';
		if( empty( $custom_post_category ) ) $custom_post_category = 'Category';

		// Form fields.
		echo '<table class="form-table">';

		echo '	<tr>';
		echo '		<th><label for="custom_author name" class="custom_author name_label">' . __( 'author', 'text_domain' ) . '</label></th>';
		echo '		<td>';
		echo '			<textarea id="custom_author name" name="custom_author name" class="custom_author name_field" placeholder="' . esc_attr__( 'author', 'text_domain' ) . '">' . $custom_author name . '</textarea>';
		echo '			<p class="description">' . __( 'Author Name', 'text_domain' ) . '</p>';
		echo '		</td>';
		echo '	</tr>';

		echo '	<tr>';
		echo '		<th><label for="custom_post_date" class="custom_post_date_label">' . __( 'post date', 'text_domain' ) . '</label></th>';
		echo '		<td>';
		echo '			<input type="date" id="custom_post_date" name="custom_post_date" class="custom_post_date_field" placeholder="' . esc_attr__( 'post date', 'text_domain' ) . '" value="' . esc_attr__( $custom_post_date ) . '">';
		echo '			<p class="description">' . __( 'Post Date', 'text_domain' ) . '</p>';
		echo '		</td>';
		echo '	</tr>';

		echo '	<tr>';
		echo '		<th><label for="custom_post_category" class="custom_post_category_label">' . __( 'Category', 'text_domain' ) . '</label></th>';
		echo '		<td>';
		echo '			<input type="text" id="custom_post_category" name="custom_post_category" class="custom_post_category_field" placeholder="' . esc_attr__( 'Category', 'text_domain' ) . '" value="' . esc_attr__( $custom_post_category ) . '">';
		echo '			<p class="description">' . __( 'Post Category', 'text_domain' ) . '</p>';
		echo '		</td>';
		echo '	</tr>';

		echo '</table>';

	}

	public function save_metabox( $post_id, $post ) {

		// Sanitize user input.
		$custom_new_author name = isset( $_POST[ 'custom_author name' ] ) ? sanitize_text_field( $_POST[ 'custom_author name' ] ) : '';
		$custom_new_post_date = isset( $_POST[ 'custom_post_date' ] ) ? sanitize_text_field( $_POST[ 'custom_post_date' ] ) : '';
		$custom_new_post_category = isset( $_POST[ 'custom_post_category' ] ) ? sanitize_text_field( $_POST[ 'custom_post_category' ] ) : '';

		// Update the meta field in the database.
		update_post_meta( $post_id, 'custom_author name', $custom_new_author name );
		update_post_meta( $post_id, 'custom_post_date', $custom_new_post_date );
		update_post_meta( $post_id, 'custom_post_category', $custom_new_post_category );

	}

}

new Custom_Meta_Box;