Inventory_Presser_Order_By_Widget::form( array $instance )

	public function form( $instance ) {
		$title = ( isset( $instance['title'] ) ? $instance['title'] : '' );
		?>
		 <p>
		  <label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:', 'inventory-presser' ); ?></label>
		  <input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo $title; ?>" />
		</p>
		<?php
		$args                   = array(
			'public' => true,
		);
		$already_turned_on_keys = array();
		if ( isset( $instance['post-meta-keys'] ) ) {
			$already_turned_on_keys = explode( '|', $instance['post-meta-keys'] );
		}

		echo '<p>Which fields should users be allowed to use as sort fields?</p>'
		. '<dl>';

		foreach ( $this->get_post_meta_keys_and_labels( $instance ) as $key => $label ) {
			// output checkbox for each one
			echo '<dt>';
			$title = 'Allow users to order by ' . $key; // title attribute for checkbox and label
			echo '<input type="checkbox" id="' . $this->get_field_id( 'obpm-key-' . $key )
			. '" name="obpm-key-' . $key . '"';
			if ( in_array( $key, $already_turned_on_keys ) ) {
				echo ' checked="checked"';
			}
			echo ' title="' . $title . '"/>'
			. '<label for="' . $this->get_field_id( 'obpm-key-' . $key ) . '" title="' . $title . '">' . $this->prettify_meta_key( $key ) . '</label>'
			. '</dt>' // and a text box for a label
			. '<dd>'
			. '<label for="' . $this->get_field_id( 'obpm-label-' . $key ) . '">Label</label> '
			. '<input type="text" id="' . $this->get_field_id( 'obpm-label-' . $key ) . '"'
			. ' name="obpm-label-' . $key . '" '
			. 'value="' . $label . '" title="Label for ' . $key . '" />'
			. '</dd>';
		}
		echo '</dl>';
	}