A relatively simple way to replace URL for media files in WordPress when running a Staging environment

functions.php

<?php

define( 'STAGING_URL', 'https://staging.mysiteurl.com');
define( 'PRODUCTION_URL', 'https://www.mysiteurl.com');

add_filter( 'wp_get_attachment_url', 'yanco_staging_wp_get_attachment_url', 1000000, 2 );
function yanco_staging_wp_get_attachment_url( $url, $attachment )
{
	if( strpos( $url, STAGING_URL ) !== false ) {
		$url = str_replace( STAGING_URL, PRODUCTION_URL, $url );
	}
	
	return $url;
}

add_filter( 'wp_get_attachment_image_attributes', 'yanco_staging_wp_get_attachment_image_attributes' );
function yanco_staging_wp_get_attachment_image_attributes($attributes)
{

    if ( isset( $attributes['src'] ) ) {
		if( strpos( $attributes['src'], STAGING_URL ) !== false ) {
			$attributes['src'] = str_replace( STAGING_URL, PRODUCTION_URL, $attributes['src'] );
		}
	}
	
	if ( isset( $attributes['srcset'] ) ) {
		if( strpos( $attributes['srcset'], STAGING_URL ) !== false ) {
			$attributes['srcset'] = str_replace( STAGING_URL, PRODUCTION_URL, $attributes['srcset'] );
		}
	}

    return $attributes;
}