Upgrade to 3.4 error: Call to undefined function get_option()

The problem was caused by about 8 wordpress files in the root directory with a filesize of 0 bytes.

Uploading fresh copies of these files (from the latest version downloaded from wordpress.org) solved the initial problem.

The subsequent problem has since cleared without any indication of what steps solved it.

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Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)