Add a custom attribute to the 'caption' shortcode

add-figure-attribute.php

<?php
/**
 * Add custom attribute to the 'caption' shortcode
 *
 * ex:
 * [caption id="attachment_883" align="alignnone" width="259" use_figure="yes"]<a href="image.jpg"><img class="size-full wp-image-883" alt="This is a caption." src="image.jpg" width="259" height="195" /></a> This is a caption.[/caption]
 * 
 * @param   array 	$out  		The output array of shortcode attributes
 * @param 	array 	$pairs		The array of accepted parameters and their defaults
 * @param 	array 	$atts 		The input array of shortcode attributes
 */
function add_custom_caption_attribute( $out, $pairs, $atts ) {
    $out['use_figure'] = '';
    return $out;
}
add_filter( 'shortcode_atts_caption', 'add_custom_caption_attribute', 10, 3 );
/**
 * Detect if the 'use_figure' custom attribute has been set to 'yes'
 * If so, output a figure/figcaption elemente rather than the default
 * div format
 * 
 * @param  	string 	$input 		Blank string
 * @param  	array  	$atts    	Shortcode attributes
 * @param  	string 	$content 	Content within the shortcode wrappers
 * @return 	string          		Formatted output
 */
function override_caption_shortcode( $input, $atts, $content ) {

    if( isset( $atts['use_figure'] ) && 'yes' == $atts['use_figure'] ) {

		extract(shortcode_atts(array(
			'id'	=> '',
			'align'	=> 'alignnone',
			'width'	=> '',
			'caption' => ''
		), $atts, 'caption'));

		if ( 1 > (int) $width || empty($caption) )
			return $content;

		if ( $id ) $id = 'id="' . esc_attr($id) . '" ';

		return '<figure ' . $id . 'class="wp-caption ' . esc_attr($align) . '" style="width: ' . (10 + (int) $width) . 'px">'
			. do_shortcode( $content ) . '<figcaption class="wp-caption-text">' . $caption . '</figcaption></figure>';
        
    }

}
add_filter( 'img_caption_shortcode', 'override_caption_shortcode', 10, 3 );