Merge Two prestashop web sites into one multi shop website (ps 1.5.x)

Let's start by pre-conditions
www1 and www2  are two websites using ps 1.5.x
=> then we have two domains (or domain and subdomain ), 2 databases and 2 prestashop working folders.

how merge ?

1- login on BO of www1
2- Activate multishop support (preferences-> generales) (may be translated) and register
3- Now may see a new menu item "multi-shop" in advanced parameters menu.

now ps is ready to work on multishop  mode

4- copy the theme of www2 in the themes directory of www1
    => if the theme of www2 (the second web site) has the same name as the first one, you must change its name then (let say 'theme2')

5- Now enter the menu item multi-shop (step 3)

you will see at the left a tree but with only one item (the name of www1)

6- Click add a shop
  i- enter the name of your site (www2)
  ii- let the two combos as they are
  iii- choose the theme (step 4 normally)
   you may then choose a least one category (default) from the tree of categories
 iv- import data ? no
Register.

Now we have to link our shop to its  url
7- Click add link
 enter web site surl of site www2 (exp: www.mysite2.com) in both http and ssl modes
Register

8- Don't forget to activate url rewriting !
(preferences -> SEO and URLs )

Great now it will not work surely :)



9- What's the problem ?
We are searching to merge data and files => one BO (back office) and one global folder containing the two sites.
Solution:
In Cpanel /plesk/etc ....
www1 -> xxx/public_html/www1
www2-> xxx/public_html/www1