Two types of comments are allowed: C-style, enclosed between ‘/*’ and ‘*/’, and shell-style, starting with ‘#’ character and extending up to the end of line:
/* This is a comment. */ # And this too.
There are, however, several special cases, where the characters following ‘#’ are not ignored:
If the first line begins with ‘#!/’ or ‘#! /’, this is treated as a start of a multi-line comment, which is closed by the characters ‘!#’ on a line by themselves. This feature allows for writing sophisticated scripts. See top-block, for a detailed description.
A ‘#’ is followed by ‘include’, ‘include_once’, ‘line’, ‘error’, or ‘warning’ is treated specially. These cases are covered by the subsequent sections.