Site hacked – now finding base64 within certain php files ….

Recently I discovered a site I worked on was hacked ? presumably ….

On google – now it comes up as a credit agency / debt management company ? only google however – not bing. Google has reevaluated it – and it still showing the wrong details

I started looking into the site to see what was causing this and the only thing I discovered is there where 2 new admins and base64 encoding on two of the .php docs

the base64 was as follows :

[Code moderated. Please do not post hack code blocks in the forums.]

Can anyone help me decode and ultimately remove this ? Or at least tell me if this is what is causing the strange goolgle listings

Shall I just delete everything – and put a clean wordpress install up there – and start from scratch ….

thankyou my dears in advance

Beebs x