Some files that IH modifies are core files. This means that IH overwrites the existing files that Zen uses. If your site has no modifications to these files then there are no problems. If your installation has existing modifications to you files then you will have to carefully merge the existing modifications with the modifications that IH makes. There are a number of ways of approaching this.

As always the best recommendation is to do this on a development version of your site. If you are serious about running your store it is always worth having a second version of the store so that you can experiment on that first. I know that this seems like a lot of work but it really is worth it and does not actually take that much time.

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Route 1

This works for installations that have no modifications.

Just install IH and it will work. If your admin is in a language other than english then read this thread for instructions.
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Route 2

This works well if you know that you have files to merge and is a good option if you don't know if you have merges to do.

Install as normal. The installer will create backups of any files it overwrites. So, just go for it. Then check your site. If everything is working well then you are good to go and you didn't need to do merges.

If problems have been created it probably means that you have merges to do. So, you can look on the server and find the backup versions of the files that have been created. Download the backup version (this will have your previous modifications). Download the active version ( this will have the IH modifications) . Merge these two files and upload the result as the active file.


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Route 3

This is the way to go if you know that you have merges to do.

Read Diva's post above and see which IH files are equivilant to which Zen files. It is not a complex pattern! Then merge your modifications into the appropriate file in the IH installation files.

For instance if you have existing modifications in

/YOUR_ADMIN/includes/modules/category_product_listing.php

merge them with the installation file

/YOUR_ADMIN/includes/modules/category_product_listing_IH4.php

Then install as normal.

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What happens during install is this:

  • The files are uploaded to the 'wrong' place.
  • A backup of your existing files is created
  • Then your files are overwritten


The logic is based on the fact that less experienced users have been known to upload files and overwrite existing file modifications. And those modifications may or may not be correctly backed up. There is potentially no recovery from this. Creating a backup before overwrite means that recovery is possible. However, to allow files to be backed up the IH files cannot be uploaded into the 'right' place because that is potentially destructive. So, they are put in an alternate position and then moved into the right place once the backup has been created.