UnPHP.net decodes many obfuscation methods used in scripts saving you time manually decoding files.
UnPHP easily handles simple obfuscation methods that chain functions like eval(), gzinflate(), str_rot13(), str_replace() and base64_decode(), the timesaver is it loops recursively through PHP code to decode multiple levels of obfuscation. even 81 rounds of eval() + base64_decode() & handles custom decoder functions and regular expressions.
The most common file you would need decoding would be a wordpress footer file to check for any included malware, UnPHP is a great tool for this. Paste your encoded wordpress footer file here http://www.unphp.net/ and then download the decoded version, now you can edit the code removing any unwanted content.