1======================== 2 PHP Coding Standards 3======================== 4 5This file lists several standards that any programmer adding or changing 6code in PHP should follow. Since this file was added at a very late 7stage of the development of PHP v3.0, the code base does not (yet) fully 8follow it, but it's going in that general direction. Since we are now 9well into version 5 releases, many sections have been recoded to use 10these rules. 11 12Code Implementation 13------------------- 14 150. Document your code in source files and the manual. [tm] 16 171. Functions that are given pointers to resources should not free them 18 19For instance, ``function int mail(char *to, char *from)`` should NOT free 20to and/or from. 21Exceptions: 22 23- The function's designated behavior is freeing that resource. E.g. efree() 24 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) 28 29- Low-level parser routines, that are tightly integrated with the token 30 cache and the bison code for minimum memory copying overhead. 31 322. 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 35 possible. 36 373. 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. 42 434. 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 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()) 51 525. 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, 54 try avoiding it. 55 566. 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 59 you're calling. 60 617. When commenting out code using a #if statement, do NOT use 0 only. Instead 62 use "<git username here>_0". For example, #if FOO_0, where FOO is your 63 git user foo. This allows easier tracking of why code was commented out, 64 especially in bundled libraries. 65 668. 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 71 729. 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. 77 78 In almost all cases, memory returned to the engine must be allocated 79 using emalloc(). 80 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. 84 85User Functions/Methods Naming Conventions 86------------------ 87 881. 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:: 93 94 Good: 95 'mcrypt_enc_self_test' 96 'mysql_list_fields' 97 98 Ok: 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'?) 103 104 Bad: 105 'hw_GetObjectByQueryCollObj' 106 'pg_setclientencoding' 107 'jf_n_s_i' 108 1092. 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 112 of ``parent_*``:: 113 114 A family of 'foo' functions, for example: 115 Good: 116 'foo_select_bar' 117 'foo_insert_baz' 118 'foo_delete_baz' 119 120 Bad: 121 'fooselect_bar' 122 'fooinsertbaz' 123 'delete_foo_baz' 124 1253. 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'. 129 1304. 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++) ...). 133 1345. Variable names should be in lowercase. Use underscores to separate 135 between words. 136 1376. 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:: 141 142 Good: 143 'connect()' 144 'getData()' 145 'buildSomeWidget()' 146 147 Bad: 148 'get_Data()' 149 'buildsomewidget' 150 'getI()' 151 1527. 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 (CamelCaps 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):: 157 158 Good: 159 'Curl' 160 'FooBar' 161 162 Bad: 163 'foobar' 164 'foo_bar' 165 166Internal Function Naming Convensions 167---------------------- 168 1691. Functions that are part of the external API should be named 170 'php_modulename_function()' to avoid symbol collision. They should be in 171 lowercase, with words underscore delimited. Exposed API must be defined 172 in 'php_modulename.h'. 173 174 PHPAPI char *php_session_create_id(PS_CREATE_SID_ARGS); 175 176 Unexposed module function should be static and should not be defined in 177 'php_modulename.h'. 178 179 static int php_session_destroy(TSRMLS_D) 180 1812. Main module source file must be named 'modulename.c'. 182 1833. Header file that is used by other sources must be named 'php_modulename.h'. 184 185 186Syntax and indentation 187---------------------- 188 1891. Never use C++ style comments (i.e. // comment). Always use C-style 190 comments instead. PHP is written in C, and is aimed at compiling 191 under any ANSI-C compliant compiler. Even though many compilers 192 accept C++-style comments in C code, you have to ensure that your 193 code would compile with other compilers as well. 194 The only exception to this rule is code that is Win32-specific, 195 because the Win32 port is MS-Visual C++ specific, and this compiler 196 is known to accept C++-style comments in C code. 197 1982. Use K&R-style. Of course, we can't and don't want to 199 force anybody to use a style he or she is not used to, but, 200 at the very least, when you write code that goes into the core 201 of PHP or one of its standard modules, please maintain the K&R 202 style. This applies to just about everything, starting with 203 indentation and comment styles and up to function declaration 204 syntax. Also see Indentstyle. 205 206 Indentstyle: http://www.catb.org/~esr/jargon/html/I/indent-style.html 207 2083. Be generous with whitespace and braces. Keep one empty line between the 209 variable declaration section and the statements in a block, as well as 210 between logical statement groups in a block. Maintain at least one empty 211 line between two functions, preferably two. Always prefer:: 212 213 if (foo) { 214 bar; 215 } 216 217 to: 218 219 if(foo)bar; 220 2214. When indenting, use the tab character. A tab is expected to represent 222 four spaces. It is important to maintain consistency in indenture so 223 that definitions, comments, and control structures line up correctly. 224 2255. Preprocessor statements (#if and such) MUST start at column one. To 226 indent preprocessor directives you should put the # at the beginning 227 of a line, followed by any number of whitespace. 228 229Testing 230------- 231 2321. Extensions should be well tested using *.phpt tests. Read about that 233 in README.TESTING. 234 235Documentation and Folding Hooks 236------------------------------- 237 238In order to make sure that the online documentation stays in line with 239the code, each user-level function should have its user-level function 240prototype before it along with a brief one-line description of what the 241function does. It would look like this:: 242 243 /* {{{ proto int abs(int number) 244 Returns the absolute value of the number */ 245 PHP_FUNCTION(abs) 246 { 247 ... 248 } 249 /* }}} */ 250 251The {{{ symbols are the default folding symbols for the folding mode in 252Emacs and vim (set fdm=marker). Folding is very useful when dealing with 253large files because you can scroll through the file quickly and just unfold 254the function you wish to work on. The }}} at the end of each function marks 255the end of the fold, and should be on a separate line. 256 257The "proto" keyword there is just a helper for the doc/genfuncsummary script 258which generates a full function summary. Having this keyword in front of the 259function prototypes allows us to put folds elsewhere in the code without 260messing up the function summary. 261 262Optional arguments are written like this:: 263 264 /* {{{ proto object imap_header(int stream_id, int msg_no [, int from_length [, int subject_length [, string default_host]]]) 265 Returns a header object with the defined parameters */ 266 267And yes, please keep the prototype on a single line, even if that line 268is massive. 269 270New and Experimental Functions 271----------------------------------- 272To reduce the problems normally associated with the first public 273implementation of a new set of functions, it has been suggested 274that the first implementation include a file labeled 'EXPERIMENTAL' 275in the function directory, and that the functions follow the 276standard prefixing conventions during their initial implementation. 277 278The file labelled 'EXPERIMENTAL' should include the following 279information:: 280 281 Any authoring information (known bugs, future directions of the module). 282 Ongoing status notes which may not be appropriate for Git comments. 283 284In general new features should go to PECL or experimental branches until 285there are specific reasons for directly adding it to the core distribution. 286 287Aliases & Legacy Documentation 288----------------------------------- 289You may also have some deprecated aliases with close to duplicate 290names, for example, somedb_select_result and somedb_selectresult. For 291documentation purposes, these will only be documented by the most 292current name, with the aliases listed in the documentation for 293the parent function. For ease of reference, user-functions with 294completely different names, that alias to the same function (such as 295highlight_file and show_source), will be separately documented. The 296proto should still be included, describing which function is aliased. 297 298Backwards compatible functions and names should be maintained as long 299as the code can be reasonably be kept as part of the codebase. See 300/phpdoc/README for more information on documentation. 301
