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PHP Coding Standards

CiviCRM uses the Drupal Coding Standards as a basis for the coding standards used in civicrm-core code and in civicrm-drupal code. The standards are version-independent and all new code should follow the current standards regardless of version.

Brief example

/**
 * The example class demonstrates Drupal/Civi code convention.
 */
class CRM_Coding_Example implements CRM_Coding_ExampleInterface {

  /**
   * Increase the size of a file exponentially.
   *
   * @param string $file
   *   The full file path. (Ex: '/tmp/myfile.txt')
   * @param int $power
   *   The number of times to double the size.
   * @return bool
   *   Whether the operation succeeded.
   */
  public function expandFile($file, $power) {
    $keyValuePairs = array(
      'first' => 1,
      'second' => 2,
    );

    if ($power < 4) {
      echo "You got it, boss.\n";
    }
    elseif ($power < 10) {
      echo "Whoa, that's gonna be a big file!\n";
    }
    else {
      echo "Whoa, that's gonna be a really big file!\n";
    }

    for ($i = 0; $i < $power; $i++) {
      $oldContent = file_get_contents($file);
      if (file_put_contents($file, $oldContent . $oldContent) === FALSE) {
        return FALSE;
      }
    }

    return TRUE;
  }

}

For more details, see the full series of example snippets from drupal.org.

Deviations from the Drupal Coding Standards

There are two deviations from the Drupal Coding standards that apply in CiviCRM.

Functions and variable names

Drupal Standard

Functions and variables should be named using lowercase, and words should be separated with an underscore.

CiviCRM Standard

For existing code/files/functions, err on the side of preserving compatibility.

For new procedural code (eg api/v3/*.php), use lowercase and underscores.

For new object-oriented code:

  1. For DAO properties, use underscores. (These correspond to the DB schema - which uses underscores.)
  2. For everything else, use camelCase. See Forum Discussion

Rational for Change

The codebase includes many examples of both "lowerCamelCase" and "snake_case" for function and variable names. Changing these can be quite difficult and can break interfaces consumed by downstream.

Classes and interfaces

Drupal Standard

Classes and interfaces in Drupal take one of two forms:

  • (Common in Drupal 7) Place classes in the root/global namespace and use "UpperCamel" names (e.g. FooBarWhiz)
  • (Common in Drupal 8) Place classes in the "Drupal\" namespace using PHP 5.3 conventions (e.g. Drupal\Foo\BarWhiz)

CiviCRM Standard

Classes and interfaces in Civi take one of two forms:

  • For the CRM_ namespace, follow the PEAR convention (using underscores for pseudo-namespaces; e.g. CRM_Foo_BarWhiz).
  • For the Civi\ namespace, follow the PHP 5.3 convention (using backslashes for namespaces; e.g. Civi\Foo\BarWhiz).

Rational for Change

Changing these can be quite difficult and can break interfaces consumed by downstream. For more discussion of CRM_ and Civi\, see The Codebase.

Localization

Any string that will be displayed to the user should be wrapped in ts() to translate the string:

$string = ts("Hello, world!");

Translation strings can also include placeholders for variables:

$string = ts("Membership for %1 has been updated. The membership End Date is %2.", array(
  1 => $userDisplayName,
  2 => $endDate,
));

For more information on translation, see Translation for Developers.

Scope

The CiviCRM Coding Standard for PHP Code and Inline Documentation applies to all PHP code in the CiviCRM code base, except files under the following directories:

  1. packages/
  2. packages.orig/
  3. tools/
  4. joomla/
  5. WordPress/