Snippet to add and save custom fields in woocommerce admin area

Woocommerce custom field backend

// Display Fields
add_action( 'woocommerce_product_options_general_product_data', 'woo_add_custom_general_fields' );

// Save Fields
add_action( 'woocommerce_process_product_meta', 'woo_add_custom_general_fields_save' );

function woo_add_custom_general_fields() {

  global $woocommerce, $post;
  
  echo '<div class="options_group">';
  
// Chapters Field
woocommerce_wp_text_input( 
	array( 
		'id'                => '_chapters_field', 
		'label'             => __( 'Chapters', 'woocommerce' ), 
		'placeholder'       => '', 
		'description'       => __( 'Enter the number of chapters here.', 'woocommerce' ),
		'type'              => 'number', 
		'custom_attributes' => array(
				'step' 	=> 'any',
				'min'	=> '0'
			) 
	)
);  
	
	// Author Field
woocommerce_wp_text_input( 
	array( 
		'id'          => '_author_field', 
		'label'       => __( 'Author', 'woocommerce' ), 
		'placeholder' => 'Book Author Name Here',
		'desc_tip'    => 'true',
		
	)
);
	// Editor Field
woocommerce_wp_text_input( 
	array( 
		'id'          => '_editor_field', 
		'label'       => __( 'Editor', 'woocommerce' ), 
		'placeholder' => 'Book Editor Name Here',
		'desc_tip'    => 'true',
		
	)
	
);

	
	// Translator Field
woocommerce_wp_text_input( 
	array( 
		'id'          => '_translator_field', 
		'label'       => __( 'Translator', 'woocommerce' ), 
		'placeholder' => 'Book Translator Name Here',
		'desc_tip'    => 'true',
		
	)
);

  echo '</div>';
	
}

//Code to save all the custom meta fields 
function woo_add_custom_general_fields_save( $post_id ){
	
	// Author Field
	$woocommerce_text_field = $_POST['_author_field'];
	if( !empty( $woocommerce_text_field ) )
		update_post_meta( $post_id, '_author_field', esc_attr( $woocommerce_text_field ) );
	
	// Editor Field
	$woocommerce_text_field = $_POST['_editor_field'];
	if( !empty( $woocommerce_text_field ) )
		update_post_meta( $post_id, '_editor_field', esc_attr( $woocommerce_text_field ) );
	
	// Translator Field
	$woocommerce_text_field = $_POST['_translator_field'];
	if( !empty( $woocommerce_text_field ) )
		update_post_meta( $post_id, '_translator_field', esc_attr( $woocommerce_text_field ) );
		
	// Chapters Field
	$woocommerce_number_field = $_POST['_chapters_field'];
	if( !empty( $woocommerce_number_field ) )
		update_post_meta( $post_id, '_chapters_field', esc_attr( $woocommerce_number_field ) );
		
	// Textarea
	$woocommerce_textarea = $_POST['_textarea'];
	if( !empty( $woocommerce_textarea ) )
		update_post_meta( $post_id, '_textarea', esc_html( $woocommerce_textarea ) );
		
	// Select
	$woocommerce_select = $_POST['_select'];
	if( !empty( $woocommerce_select ) )
		update_post_meta( $post_id, '_select', esc_attr( $woocommerce_select ) );
		
	// Checkbox
	$woocommerce_checkbox = isset( $_POST['_checkbox'] ) ? 'yes' : 'no';
	update_post_meta( $post_id, '_checkbox', $woocommerce_checkbox );
	
	// Custom Field
	$custom_field_type =  array( esc_attr( $_POST['_field_one'] ), esc_attr( $_POST['_field_two'] ) );
	update_post_meta( $post_id, '_custom_field_type', $custom_field_type );
	
	// Hidden Field
	$woocommerce_hidden_field = $_POST['_hidden_field'];
	if( !empty( $woocommerce_hidden_field ) )
		update_post_meta( $post_id, '_hidden_field', esc_attr( $woocommerce_hidden_field ) );
		
	// Product Field Type
	$product_field_type =  $_POST['product_field_type'];
	update_post_meta( $post_id, '_product_field_type_ids', $product_field_type );
	
}