STRICT NOTICE errors

Hi I’m getting a lot of strict notice errors in my log file, mainly a set of them that keep repeating:

[27-Apr-2013 20:04:06] STRICT NOTICE: Declaration of W3_Cache_File_Generic::set() should be compatible with that of W3_Cache_File::set()
[27-Apr-2013 20:04:06] STRICT NOTICE: Declaration of W3_Cache_File_Generic::get() should be compatible with that of W3_Cache_File::get()
[27-Apr-2013 20:04:06] STRICT NOTICE: Declaration of W3_Cache_File_Generic::delete() should be compatible with that of W3_Cache_File::delete()
[27-Apr-2013 20:04:06] STRICT NOTICE: Declaration of OpenCloud\DNS\PtrRecord::Create() should be compatible with that of OpenCloud\DNS\DnsObject::Create()
[27-Apr-2013 20:04:06] STRICT NOTICE: Declaration of OpenCloud\DNS\PtrRecord::Update() should be compatible with that of OpenCloud\DNS\DnsObject::Update()
[27-Apr-2013 20:04:06] STRICT NOTICE: Declaration of OpenCloud\DNS\PtrRecord::Delete() should be compatible with that of OpenCloud\DNS\DnsObject::Delete()
[27-Apr-2013 20:04:06] STRICT NOTICE: Declaration of OpenCloud\DNS\PtrRecord::UpdateJson() should be compatible with that of OpenCloud\DNS\DnsObject::UpdateJson()

What could be causing this?

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