"PHP".
You're posting in a PHP forum, so your question must be about PHP. Therefore this part of the subject line is redundant.
"Help".
You're posting in a help forum, so your question must be seeking help. Therefore this part of the subject line is redundant.
"!!!!!".
Terry Pratchett (Maskerade) wrote:And all those exclamation marks, you notice? Five? A sure sign of someone who wears his underpants on his head.
Rule of thumb: The subject line should be a line giving the subject of the post.