Attachment source fields (add and save)

add-save-attachment-source-fields.php

<?php
/**
 * Attachment source fields
 * @link https://kaspars.net/?p=3203
 * @link https://www.billerickson.net/?p=3555
 * 
 */

// Add fields
add_filter( 'attachment_fields_to_edit', 'ac_attachment_fields_to_edit_source', 10, 2 );
function ac_attachment_fields_to_edit_source( $form_fields, $post ) {
	// Source URL
	$form_fields['source_url'] = array(
		'label' => esc_attr( 'Source URL' ),
		'input' => 'url',
		'value' => esc_url( get_post_meta( $post->ID, '_wp_attachment_source_url', true ) ),
	);

	// Source Name
	$form_fields['source_name'] = array(
		'label' => esc_attr( 'Source Name' ),
		'input' => 'text',
		'value' => esc_attr( get_post_meta( $post->ID, '_wp_attachment_source_name', true ) ),
	);

	return $form_fields;
}

// Save fields
add_filter( 'attachment_fields_to_save', 'ac_attachment_fields_to_save_source_url_name', 10, 2 );
function ac_attachment_fields_to_save_source_url_name( $post, $attachment ) {
	// Source URL
	if ( isset( $attachment['source_url'] ) ) {
		
		// Get previous value
		$source_url = get_post_meta( $post['ID'], '_wp_attachment_source_url', true );
		
		// If there is a change
		if ( $source_url !== $attachment['source_url'] ) {
		
			// Delete
			if ( empty( $attachment['source_url'] ) ) {
				delete_post_meta( $post['ID'], '_wp_attachment_source_url' );
			}
			// Update
			else {
				update_post_meta( $post['ID'], '_wp_attachment_source_url', $attachment['source_url'] );
			}
		
		}
	
	}
	// Source Name
	if ( isset( $attachment['source_name'] ) ) {

		// Get previous value
		$source_name = get_post_meta( $post['ID'], '_wp_attachment_source_name', true );

		// If there is a change
		if ( $source_name !== $attachment['source_name'] ) {

			// Delete
			if ( empty( $attachment['source_name'] ) ) {
				delete_post_meta( $post['ID'], '_wp_attachment_source_name' );
			}
			// Update
			else {
				update_post_meta( $post['ID'], '_wp_attachment_source_name', $attachment['source_name'] );
			}

		}

	}
	return $post;
}