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PHP Coding Standards
====================
This file lists several standards that any programmer, adding or changing
code in PHP, should follow. Since this file was added at a very late
stage of the development of PHP v3.0, the code base does not (yet) fully
follow it, but it's going in that general direction. Since we are now
at version 4.0.3, many sections have been recoded to use these rules.
Code Implementation
-------------------
[1] Functions that are given pointers to resources should not free them
For instance, function int mail(char *to, char *from) should NOT free
to and/or from.
Exceptions:
- The function's designated behavior is freeing that resource. E.g. efree()
- The function is given a boolean argument, that controls whether or not
the function may free its arguments (if true - the function must free its
arguments, if false - it must not)
- Low-level parser routines, that are tightly integrated with the token
cache and the bison code for minimum memory copying overhead.
[2] Functions that are tightly integrated with other functions within the
same module, and rely on each other non-trivial behavior, should be
documented as such and declared 'static'. They should be avoided if
possible.
[3] Use definitions and macros whenever possible, so that constants have
meaningful names and can be easily manipulated. The only exceptions
to this rule are 0 and 1, when used as false and true (respectively).
Any other use of a numeric constant to specify different behavior
or actions should be done through a #define.
[4] When writing functions that deal with strings, be sure to remember
that PHP holds the length property of each string, and that it
shouldn't be calculated with strlen(). Write your functions in a such
a way so that they'll take advantage of the length property, both
for efficiency and in order for them to be binary-safe.
Functions that change strings and obtain their new lengths while
doing so, should return that new length, so it doesn't have to be
recalculated with strlen() (e.g. php_addslashes())
[5] Use php_error() to report any errors/warnings during code execution.
Use descriptive error messages, and try to avoid using identical
error strings for different stages of an error. For example,
if in order to obtain a URL you have to parse the URL, connect,
and retreive the text, assuming something can go wrong at each
of these stages, don't report an error "Unable to get URL"
on all of them, but instead, write something like "Unable
to parse URL", "Unable to connect to URL server" and "Unable
to fetch URL text", respectively.
[6] NEVER USE strncat(). If you're absolutely sure you know what you're doing,
check its man page again, and only then, consider using it, and even then,
try avoiding it.
Naming Conventions
------------------
[1] Function names for user functions should be enclosed with in
the PHP_FUNCTION() macro. They should be in lowercase, with words
underscore delimited, with care taken to minimize the letter count.
If they are part of a "parent set" of functions, that parent should
be included in the user function name.
Good:
'mcrypt_enc_self_test'
'mysql_list_fields'
Ok:
'mcrypt_module_get_algo_supported_key_sizes'
(could be 'mcrypt_mod_get_algo_sup_key_sizes'?)
'get_html_translation_table'
(could be 'html_get_trans_table'?)
Bad:
'hw_GetObjectByQueryCollObj'
'pg_setclientencoding'
[2] Function names used by user functions should be prefixed
with "_php_", and followed by a word or an underscore-delimited list of
words, in lowercase letters, that describes the function. If applicable,
they should be declared 'static'.
[3] Variable names must be meaningful. One letter variable names must be
avoided, except for places where the variable has no real meaning or
a trivial meaning (e.g. for (i=0; i<100; i++) ...).
[4] Variable names should be in lowercase; Use underscores to seperate
between words.
Syntax and indentation
----------------------
[1] Never use C++ style comments (i.e. // comment). Always use C-style
comments instead. PHP is written in C, and is aimed at compiling
under any ANSI-C compliant compiler. Even though many compilers
accept C++-style comments in C code, you have to ensure that your
code would compile with other compilers as well.
The only exception to this rule is code that is Win32-specific,
because the Win32 port is MS-Visual C++ specific, and this compiler
is known to accept C++-style comments in C code.
[2] Use K&R-style. Of course, we can't and don't want to
force anybody to use a style she's not used to, but
at the very least, when you write code that goes into the core
of PHP or one of its standard modules, please maintain the K&R
style. This applies to just about everything, starting with
indentation and comment styles and up to function decleration
syntax.
[3] Be generous with whitespace and braces. Always prefer
if (foo) {
bar;
}
to
if(foo)bar;
Keep one empty line between the variable decleration section and
the statements in a block, as well as between logical statement
groups in a block. Maintain at least one empty line between
two functions, preferably two.
Documentation and Folding Hooks
-------------------------------
In order to make sure that the online documentation stays in line with
the code, each user-level function should have its user-level function
prototype before it along with a brief one-line description of what the
function does. It would look like this:
/* {{{ proto int abs(int number)
Return the absolute value of the number */
PHP_FUNCTION(abs)
{
...
}
/* }}} */
The {{{ symbols are the default folding symbols for the folding mode in
Emacs. vim will soon have support for folding as well. Folding is very
useful when dealing with large files because you can scroll through the
file quickly and just unfold the function you wish to work on. The }}}
at the end of each function marks the end of the fold, and should be on
a separate line.
The "proto" keyword there is just a helper for the doc/genfuncsummary script
which generates a full function summary. Having this keyword in front of the
function prototypes allows us to put folds elsewhere in the code without
messing up the function summary.
Optional arguments are written like this:
/* {{{ proto object imap_header(int stream_id, int msg_no [, int from_length [, int subject_length [, string default_host]]])
And yes, please keep everything on a single line, even if that line is massive.
Aliases & Legacy Documentation
-----------------------------------
You may also have some deprecated aliases with close to duplicate
names, for example, somedb_select_result and somedb_selectresult. For
documentation puposes, these will only be documented by the most
current name, with the aliases listed in the documentation for
the parent function. For ease of reference, user-functions with
completely different names, that alias to the same function (such as
highlight_file and show_source), will be separately documented. The
proto should still be included, describing which function is aliased.
Backwards compatible functions and names should be maintained as long
as the code can be reasonably be kept as part of the codebase. See
/phpdoc/README for me information on documentation.
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