PHP RFC: Casing of acronyms in class and method names

• Version: 1.0
• Date: 2024-04-05
• Author: Tim Düsterhus, timwolla@php.net
• Status: Draft (or Under Discussion or Accepted or Declined)
• First Published at: http://wiki.php.net/rfc/class-naming-acronyms

The results of the Class Naming RFC decided that class names should be written in PascalCase (“Upper Camel Case”), with the exception of acronyms, which should be included in UPPERCASE. This RFC proposes to revisit the prior decision, instead treating acronyms like regular words, making classnames consistent PascalCase.

The class naming policy should be updated to the following, with changes highlighted:

Method names follow the studlyCaps (also referred to as bumpy case or camel caps) naming convention, with care taken to minimize the letter count. The initial letter of the name is lowercase, and each letter that starts a new word is capitalized.

Class names should be descriptive nouns in PascalCase and as short as possible. Each word in the class name should start with a capital letter, without underscore delimiters. The class name should be prefixed with the name of the “parent set” (e.g. the name of the extension) if no namespaces are used.

Abbreviations and acronyms as well as initialisms should be avoided wherever possible, unless they are much more widely used than the long form (e.g. HTTP or URL). Abbreviations start with a capital letter followed by lowercase letters, whereas acronyms and initialisms are written according to their standard notation. Abbreviations, acronyms, and initialisms should be treated like regular words, thus they should be written with an uppercase first character, followed by lowercase characters. Usage of acronyms and initialisms is not allowed if they are not widely adopted and recognized as such.

Diverging from this policy is allowed to keep internal consistency within a single extension, if the name follows an established, language-agnostic standard, or for other reasons, if those reasons are properly justified and voted on as part of the RFC process.

Good method names:

connect()
getData()
buildSomeWidget()
performHttpRequest()

Bad method names:

get_Data()
buildsomewidget()
getI()
performHTTPRequest()

Good class names:

Curl
CurlResponse
HttpStatusCode
Url
BtreeMap // B-tree Map
Id // Identifier
ID // Identity Document
Char // Character
Intl // Internationalization

Bad class names:

curl
curl_response
HTTPStatusCode
URL
BTreeMap
ID // Identifier
CHAR
INTL

The DOM HTML5 parsing and serialization RFC introduced new class names and method names that violate the updated naming policy, should this RFC be accepted. As part of this RFC, the following changes will be made:

• The DOM namespace will be renamed to Dom, affecting everything contained within it.
• DOM\DTDNamedNodeMap -> Dom\DtdNamedNodeMap
• DOM\HTMLCollection -> Dom\HTMLCollection (Justification: The DOM Standard specifies the name)
• DOM\CDATASection -> Dom\CDATASection (Justification: The DOM Standard specifies the name)
• DOM\HTMLDocument -> Dom\HtmlDocument
• DOM\XMLDocument -> Dom\XmlDocument
• DOM\XPath -> Dom\XPath (Justification: The DOM Standard specifies the XPath interfaces that use this casing)
• DOM\Implementation::createHTMLDocument() -> Dom\Implementation::createHtmlDocument()
• DOM\Node::lookupNamespaceURI() -> Dom\Node::lookupNamespaceURI() (Justification: The DOM Standard specifies the name)
• DOM\*::*NS() -> Dom\*::*NS() (Justification: The DOM Standard generally specifies the NS suffix in this casing)
• DOM\DocumentFragment::appendXML() -> Dom\DocumentFragment::appendXml()
• DOM\Document::createCDATASection() -> Dom\Document::createCDATASection() (Justification: The DOM Standard specifies the name)
• DOM\Document::relaxNGValidate() -> Dom\Document::relaxNgValidate()
• DOM\Document::relaxNGValidateSource() -> Dom\Document::relaxNgValidateSource()
• DOM\HTMLDocument::saveXML() -> Dom\HtmlDocument::saveXml()
• DOM\HTMLDocument::saveXMLFile() -> Dom\HtmlDocument::saveXmlFile()
• DOM\HTMLDocument::saveHTML() -> Dom\HtmlDocument::saveHtml()
• DOM\HTMLDocument::saveHTMLFile() -> Dom\HtmlDocument::saveHtmlFile()
• DOM\XMLDocument::saveXML() -> Dom\XmlDocument::saveXml()
• DOM\XMLDocument::saveXMLFile() -> Dom\XmlDocument::saveXmlFile()

For the Improve callbacks in ext/dom and ext/xsl RFC the following changes will be made:

• \DOMXPath::registerPhpFunctionNS() -> \DOMXPath::registerPhpFunctionNS() (Justification: Consistency with the *NS() methods in ext/dom)
• \DOM\XPath::registerPhpFunctionNS() -> \Dom\XPath::registerPhpFunctionNS() (Justification: see above)
• \XSLTProcessor::registerPHPFunctionNS() -> \XSLTProcessor::registerPHPFunctionNS() (Justification: Consistency with \XSLTProcessor::registerPHPFunctions(), which unfortunately is inconsistent with \DOMXPath).

Existing classnames in released versions are not affected, thus there are not backwards incompatible changes. This is a policy RFC.

Next PHP 8.x (PHP 8.4).

SAPIs that expose classes should take the RFC results into account.

Extensions should take the RFC results into account.

None.

None.

None.

None.

Everything that is not a class name of an internal class. Everything that is already in PHP.

None.

Include these so readers know where you are heading and can discuss the proposed voting options.

None, yet. This RFC will result in changes to:

• https://github.com/php/php-src/blob/536305436f44e91731bc5c86e06f137e44a01109/CODING_STANDARDS.md#L173-L211
• https://github.com/php/policies/blob/main/coding-standards-and-naming.rst

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• Class Naming RFC
• Prior mailing list discussion: https://externals.io/message/120959#120959

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