8
Upgrading is probably a good idea, but you could try replacing:
set_magic_quotes_runtime(0);
with:
ini_set("magic_quotes_runtime", 0);
Deprecated basically means 'gone in the next version' so that may only work until your host upgrades PHP again. You could also try changing the PHP error reporting options by adding the following to an .htaccess file.
php_value error_reporting 1
This should restrict reporting to fatal run-time errors and unrecoverable errors, but not deprecated.
If your server path is the same as before, the login issue is probably a result of a (hopefully temporary) DNS issue with the new server address.
I personally don't have a setup where I can try any of the above, so grabbing a backup of your site folders and database would be wise before messing about too much!
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