Develop custom php in WP All Import to create image attachment in posts

I have exported data from an old site and now i use WP All Import Pro to import the data. I have a problem on importing images. - initially all images from the old site are uploaded to files in wp import files folder. - when i run all the relevant images are loaded into the media library, but are not attached to posts except for the thumbnail. WP all import gave me the following answer: "In looking at this, images are being attached to the post. The issue is that the image references in the post content are still referencing the old site. WP All Import does not currently update image references in the post content (though we plan to allow for this in the future), but in the meantime, it sounds like some custom PHP code would have to be used with our API: [login to view URL] I would not have an example snippet for this case, unfortunately, and writing custom code is outside the scope of the support we offer." End result: - after including th custom php in wp all import all images will be attached to posts. - documentation of changes must be includen