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These are the coding standards for Elgg. All core development, bundled
plugins, and tickets attached to Trac are expected to be in this format.
* Unix line endings.
* Hard tabs, 4 character tab spacing.
* No PHP shortcut tags ( <? or <?= or <% ).
* PHPDoc comments on functions and classes (all methods; declared properties
when appropriate).
* Mandatory wrapped {}s around any code blocks.
if (true)
foreach($arr as $elem)
echo $elem;
if (true) {
foreach($arr as $elem) {
echo $elem;
* Name standalone functions using underscore_character().
* Name classes using CamelCase() and methods using lowerCamelCase().
* Name globals and constants in ALL_CAPS (TRUE, NULL, ACCESS_FRIENDS, $CONFIG).
* Use underscores / camel case to separate standard English words in
functions, classes, and methods. (get_default_site(), ElggUser->isLoggedIn()).
* Space functions like_this($required, $optional = TRUE).
* Space keywords and constructs like this: if (FALSE) { ... }.
* Correctly use spaces, quotes, and {}s in strings:
Bad (hard to read, misuse of quotes and {}s):
echo 'Hello, '.$name."! How is your {$time_of_day}?";
echo "Hello, $name! How is your $time_of_day?";
* Line lengths should be reasonable. If you are writing lines over 100
characters on a line, please revise the code.
* Use // or /* */ when commenting.
* No closing PHP tag (?>) at EOF unless after a heredoc. (Avoids problems with
trailing whitespace. Required after heredoc by PHP.)
The following best practices make code easier to read, easier to maintain,
and easier to debug. Consistent use of these guidelines means less guess
work for developers, which means happier, more productive developers.
* Adhere to "Don't Repeat Yourself" (DRY) principles of code design and
organization. If you are copy-and-pasting code YOU ARE DOING SOMETHING WRONG.
If you find a block of code that you want to use multiple times, make a
function. If you find views that are identical except for a single value,
pull it out into a generic view that takes an option.
* Whitespace is free. Don't be afraid to use it to separate blocks of code.
Use a single space to separate function params and string concatenation.
* Use self-documenting variable names. $group_guids is better than $array.
* Functions returning an array should return an empty array instead of FALSE
on no results.
* Functions not throwing an exception on error should return FALSE upon
* Functions returning only boolean should be prefaced with is_ or has_ (eg,
is_logged_in(), has_access_to_entity()).
* Ternary syntax is acceptable for single-line, non-embedded statements.
* Use comments effectively. Good comments describe the "why." Good code
describes the "how." Ex:
Not a very useful comment:
// increment $i only when the entity is marked as active.
foreach($entities as $entity) {
if ($entity->active == TRUE) {
Useful comment:
// find the next index for inserting a new active entity.
foreach($entities as $entity) {
if ($entity->active == TRUE) {
* Use commit messages effectively. Be concise and meaningful. Ex:
Not meaningful:
Small fix to groups.
Fixes #1234: Added missing ) that caused a WSOD on group profile page
when logged out.
* Commit effectively: Err on the side of atomic commits. One revision with
many changes is scary.
Occasionally, functions and classes must be deprecated in favor of newer
replacements. Since 3rd party plugin authors rely on a consistent API,
backward compatibility must be maintained, but will not be maintained
indefinitely as plugin authors are expected to properly update their
plugins. In order to maintain backward compatibility, deprecated APIs will
follow these guidelines:
* Incompatible API changes cannot occur between bugfix versions
(1.6.0 - 1.6.1).
* API changes between minor versions (1.6 - 1.7) must maintain backward
compatibility for at least 2 minor versions. (1.7 and 1.8. See
procedures, below.)
* Bugfixes that change the API cannot be included in bugfix versions.
* API changes between major versions (1.0 - 2.0) can occur without regard to
backward compatibility.
The procedure for deprecating an API is as follows:
* The first minor version (1.7) with a deprecated API must include a wrapper
function/class (or otherwise appropriate means) to maintain backward
compatibility, including any bugs in the original function/class.
This compatibility layer uses elgg_deprecated_notice('...', 1.7) to log
that the function is deprecated.
* The second minor version (1.8) maintains the backward compatibility
layer, but elgg_deprecated_notice() will produce a visible warning.
* The third minor version (1.9) removes the compatibility layer. Any use of
the deprecated API should be corrected before this.
The general timeline for two minor releases is 8 to 12 months.
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