Filter captioned images to include source link

source-link-captioned-images.php

<?php
/**
 * Filter captioned images to include source link
 *
 * @link https://core.trac.wordpress.org/browser/trunk/src/wp-includes/media.php (img_caption_shortcode)
 * 
 */
add_filter( 'img_caption_shortcode', 'ac_add_sources_captioned', 10, 3 );

function ac_add_sources_captioned( $empty, $attr, $content ) {

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

	$post_id = explode( '_', esc_attr( $atts['id'] ) );

	$source_url = get_post_meta( $post_id[1], '_wp_attachment_source_url', true );

	// We have a source
	if ( ! empty( $source_url ) ) {

		// Source name
		$source_name = get_post_meta( $post_id[1], '_wp_attachment_source_name', true );

		if ( empty( $source_name ) ) {

			$parsed_url = parse_url( $source_url );

			$source_name = str_replace( 'www.', '', $parsed_url['host'] );

		}

		// Code from /wp-includes/media.php
		$atts['width'] = (int) $atts['width'];
		if ( $atts['width'] < 1 || empty( $atts['caption'] ) ) {
			return $content;
		}

		if ( ! empty( $atts['id'] ) ) {
			$atts['id'] = 'id="' . esc_attr( $atts['id'] ) . '" ';
		}
		
		$class = trim( 'wp-caption ' . $atts['align'] . ' ' . $atts['class'] );

		// Return output along with source
		return '<figure ' . $atts['id'] . 'style="width: ' . (int) $atts['width'] . 'px;" class="' . esc_attr( $class ) . '"><span class="image-wrap">' . do_shortcode( $content ) . '<span class="source"><a href="' . esc_url( $source_url ) . '" target="_blank">' . $source_name . '</a></span></span><figcaption class="wp-caption-text">' . $atts['caption'] . '</figcaption></figure>';

	}
	// No source
	else {

		return '';

	}

}