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5 This file lists several standards that any programmer adding or changing
6 code in PHP should follow. Since this file was added at a very late
7 stage of the development of PHP v3.0, the code base does not (yet) fully
8 follow it, but it's going in that general direction. Since we are now
9 well into version 5 releases, many sections have been recoded to use
15 0. Document your code in source files and the manual. [tm]
17 1. Functions that are given pointers to resources should not free them
19 For instance, ``function int mail(char *to, char *from)`` should NOT free
23 - The function's designated behavior is freeing that resource. E.g. efree()
25 - The function is given a boolean argument, that controls whether or not
26 the function may free its arguments (if true - the function must free its
27 arguments, if false - it must not)
29 - Low-level parser routines, that are tightly integrated with the token
30 cache and the bison code for minimum memory copying overhead.
32 2. Functions that are tightly integrated with other functions within the
33 same module, and rely on each other non-trivial behavior, should be
34 documented as such and declared 'static'. They should be avoided if
37 3. Use definitions and macros whenever possible, so that constants have
38 meaningful names and can be easily manipulated. The only exceptions
39 to this rule are 0 and 1, when used as false and true (respectively).
40 Any other use of a numeric constant to specify different behavior
41 or actions should be done through a #define.
43 4. When writing functions that deal with strings, be sure to remember
44 that PHP holds the length property of each string, and that it
45 shouldn't be calculated with strlen(). Write your functions in a such
46 a way so that they'll take advantage of the length property, both
47 for efficiency and in order for them to be binary-safe.
48 Functions that change strings and obtain their new lengths while
49 doing so, should return that new length, so it doesn't have to be
50 recalculated with strlen() (e.g. php_addslashes())
52 5. NEVER USE strncat(). If you're absolutely sure you know what you're doing,
53 check its man page again, and only then, consider using it, and even then,
56 6. Use ``PHP_*`` macros in the PHP source, and ``ZEND_*`` macros in the Zend
57 part of the source. Although the ``PHP_*`` macro's are mostly aliased to the
58 ``ZEND_*`` macros it gives a better understanding on what kind of macro
61 7. When commenting out code using a #if statement, do NOT use 0 only. Instead
62 use "<svn username here>_0". For example, #if FOO_0, where FOO is your
63 svn user foo. This allows easier tracking of why code was commented out,
64 especially in bundled libraries.
66 8. Do not define functions that are not available. For instance, if a
67 library is missing a function, do not define the PHP version of the
68 function, and do not raise a run-time error about the function not
69 existing. End users should use function_exists() to test for the
70 existence of a function
72 9. Prefer emalloc(), efree(), estrdup(), etc. to their standard C library
73 counterparts. These functions implement an internal "safety-net"
74 mechanism that ensures the deallocation of any unfreed memory at the
75 end of a request. They also provide useful allocation and overflow
76 information while running in debug mode.
78 In almost all cases, memory returned to the engine must be allocated
81 The use of malloc() should be limited to cases where a third-party
82 library may need to control or free the memory, or when the memory in
83 question needs to survive between multiple requests.
88 1. Function names for user-level functions should be enclosed with in
89 the PHP_FUNCTION() macro. They should be in lowercase, with words
90 underscore delimited, with care taken to minimize the letter count.
91 Abbreviations should not be used when they greatly decrease the
92 readability of the function name itself::
95 'mcrypt_enc_self_test'
99 'mcrypt_module_get_algo_supported_key_sizes'
100 (could be 'mcrypt_mod_get_algo_sup_key_sizes'?)
101 'get_html_translation_table'
102 (could be 'html_get_trans_table'?)
105 'hw_GetObjectByQueryCollObj'
106 'pg_setclientencoding'
109 2. If they are part of a "parent set" of functions, that parent should
110 be included in the user function name, and should be clearly related
111 to the parent program or function family. This should be in the form
114 A family of 'foo' functions, for example:
125 3. Function names used by user functions should be prefixed
126 with ``_php_``, and followed by a word or an underscore-delimited list of
127 words, in lowercase letters, that describes the function. If applicable,
128 they should be declared 'static'.
130 4. Variable names must be meaningful. One letter variable names must be
131 avoided, except for places where the variable has no real meaning or
132 a trivial meaning (e.g. for (i=0; i<100; i++) ...).
134 5. Variable names should be in lowercase. Use underscores to separate
137 6. Method names follow the 'studlyCaps' (also referred to as 'bumpy case'
138 or 'camel caps') naming convention, with care taken to minimize the
139 letter count. The initial letter of the name is lowercase, and each
140 letter that starts a new 'word' is capitalized::
152 7. Classes should be given descriptive names. Avoid using abbreviations where
153 possible. Each word in the class name should start with a capital letter,
154 without underscore delimiters (CampelCaps starting with a capital letter).
155 The class name should be prefixed with the name of the 'parent set' (e.g.
156 the name of the extension)::
166 Syntax and indentation
167 ----------------------
169 1. Never use C++ style comments (i.e. // comment). Always use C-style
170 comments instead. PHP is written in C, and is aimed at compiling
171 under any ANSI-C compliant compiler. Even though many compilers
172 accept C++-style comments in C code, you have to ensure that your
173 code would compile with other compilers as well.
174 The only exception to this rule is code that is Win32-specific,
175 because the Win32 port is MS-Visual C++ specific, and this compiler
176 is known to accept C++-style comments in C code.
178 2. Use K&R-style. Of course, we can't and don't want to
179 force anybody to use a style he or she is not used to, but,
180 at the very least, when you write code that goes into the core
181 of PHP or one of its standard modules, please maintain the K&R
182 style. This applies to just about everything, starting with
183 indentation and comment styles and up to function declaration
184 syntax. Also see Indentstyle_.
186 .. _Indentstyle: http://www.catb.org/~esr/jargon/html/I/indent-style.html
188 3. Be generous with whitespace and braces. Keep one empty line between the
189 variable declaration section and the statements in a block, as well as
190 between logical statement groups in a block. Maintain at least one empty
191 line between two functions, preferably two. Always prefer::
201 4. When indenting, use the tab character. A tab is expected to represent
202 four spaces. It is important to maintain consistency in indenture so
203 that definitions, comments, and control structures line up correctly.
205 5. Preprocessor statements (#if and such) MUST start at column one. To
206 indent preprocessor directives you should put the # at the beginning
207 of a line, followed by any number of whitespace.
212 1. Extensions should be well tested using *.phpt tests. Read about that
215 Documentation and Folding Hooks
216 -------------------------------
218 In order to make sure that the online documentation stays in line with
219 the code, each user-level function should have its user-level function
220 prototype before it along with a brief one-line description of what the
221 function does. It would look like this::
223 /* {{{ proto int abs(int number)
224 Returns the absolute value of the number */
231 The {{{ symbols are the default folding symbols for the folding mode in
232 Emacs and vim (set fdm=marker). Folding is very useful when dealing with
233 large files because you can scroll through the file quickly and just unfold
234 the function you wish to work on. The }}} at the end of each function marks
235 the end of the fold, and should be on a separate line.
237 The "proto" keyword there is just a helper for the doc/genfuncsummary script
238 which generates a full function summary. Having this keyword in front of the
239 function prototypes allows us to put folds elsewhere in the code without
240 messing up the function summary.
242 Optional arguments are written like this::
244 /* {{{ proto object imap_header(int stream_id, int msg_no [, int from_length [, int subject_length [, string default_host]]])
245 Returns a header object with the defined parameters */
247 And yes, please keep the prototype on a single line, even if that line
250 New and Experimental Functions
251 -----------------------------------
252 To reduce the problems normally associated with the first public
253 implementation of a new set of functions, it has been suggested
254 that the first implementation include a file labeled 'EXPERIMENTAL'
255 in the function directory, and that the functions follow the
256 standard prefixing conventions during their initial implementation.
258 The file labelled 'EXPERIMENTAL' should include the following
261 Any authoring information (known bugs, future directions of the module).
262 Ongoing status notes which may not be appropriate for SVN comments.
264 Aliases & Legacy Documentation
265 -----------------------------------
266 You may also have some deprecated aliases with close to duplicate
267 names, for example, somedb_select_result and somedb_selectresult. For
268 documentation purposes, these will only be documented by the most
269 current name, with the aliases listed in the documentation for
270 the parent function. For ease of reference, user-functions with
271 completely different names, that alias to the same function (such as
272 highlight_file and show_source), will be separately documented. The
273 proto should still be included, describing which function is aliased.
275 Backwards compatible functions and names should be maintained as long
276 as the code can be reasonably be kept as part of the codebase. See
277 /phpdoc/README for more information on documentation.