The following list gives an overview of which rights the PHP project
reserves for itself, when choosing names for new internal identifiers.
The definitive guide is the official
» CODING STANDARDS:
PHP owns the top-level namespace but tries to find decent descriptive
names and avoid any obvious clashes.
Function names use underscores between words, while class names use
the camel case rule (there are some exceptions for older
classes and functions).
PHP will prefix any global symbols of an extension with the name of
the extension. (In the past, there have been numerous
exceptions to this rule.) Examples:
strpos() (example of a past mistake)
Iterators and Exceptions are however simply postfixed with
"Iterator" and "Exception."
PHP reserves all symbols starting with __
as magical. It is recommended that you do not create symbols starting
with __ in PHP unless
you want to use documented magical functionality. Examples: