Slow BackOffice in Prestashop 1.5.5 and Prestashop 1.5.6

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Slow BackOffice in Prestashop 1.5.5 and Prestashop 1.5.6 is happens to my fresh installation of prestashop on my server. The front office is okay, its not having a load time issue, but the backoffice is very slow.
When i turn on the debugging on my backoffice, i got this results :

Load time: 15.205s
You'd better run your shop on a toaster
  • config: 80ms
  • constructor: 0ms
  • init: 10ms
  • checkAccess: 0ms
  • setMedia: 2ms
  • postProcess: 0ms
  • initHeader: 5ms
  • initContent: 15.101s
  • initFooter: 0ms
  • display: 7ms

To see what is the problems that make your prestashop backoffice slowing down, you must ensure couple of things :
  • Make sure are folder permission are 755 and 644 for files
  • Turn on the debug mode on my prestashop to see if there any error on your prestashop installation.
 After a closer look, and compare the files i noticed that upon installation of Prestashop, there are some XML-files downloaded from (api.prestashop.com or/and api.addons.prestashop.com). Those are put into config/xml-folder. Also with that there are some tables created. I had no xml-files and only 236 tables instead of 244.

 You could try to create a new prestashop installation just in case your server block those domain (api.prestashop.com or/and api.addons.prestashop.com), or your could copy the xml files from others prestashop installation.

For those of you who are using prestashop 1.6.1.1 and got slow backoffice, try to applied patch from this link