What is the best collation to use for MySQL with PHP?

Is there a collation type which is officially recommended by MySQL, for a general website where you aren't 100% sure of what will be entered? I understand that all the encodings should be the same, such as MySQL, Apache, the HTML and anything inside PHP. In the past I have set PHP to output in "UTF-8", but which collation does this match in MySQL? I'm thinking it's one of the UTF-8 ones, but I have used `utf8_unicode_ci`, `utf8_general_ci`, and `utf8_bin` before, and I do not know which of these "utf8" maps to, or if that is the best to use.