php - How do I detect if have to apply UTF-8 decode or encode on a string?

Question

I have a feed taken from third-party sites, and sometimes I have to apply utf8_decode and other times utf8_encode to get the desired visible output.

If by mistake the same stuff is applied twice/or the wrong method is used I get something more ugly, this is what I want to change.

How can I detect when what have to apply on the string?

Actually the content returns UTF-8, but inside there are parts that are not.

Answer 1

I can't say I can rely on mb_detect_encoding(). I had some freaky false positives a while back.

The most universal way I found to work well in every case was:

if (preg_match('!!u', $string))
{
   // This is UTF-8
}
else
{
   // Definitely not UTF-8
}