PHP RFC: Extended keyword support

• Version: 1.0
• Date: 2013-09-14
• Author: Bob Weinand, bobwei9@hotmail.com
• Status: Under Discussion
• First Published at: http://wiki.php.net/rfc/keywords_as_identifiers

This RFC aims to remove some restrictions which are due to the fact that keywords are not included in T_STRING (especially for class const, method and class names).

• One might want to define an HTTP agent class. And would like to store some HTTP status constants:

class HTTP {
    const CONTINUE = 100; // Works with patch
// But currently this fails with a parse error, because continue is a keyword.
    const SWITCHING_PROTOCOLS = 101;
    // etc. ...
}

• Building conditions with “and” or “or” methods

class Cond {
    public static function and (...) { // using an "and" or "or" as name currently fails
        // some logic here
        return $andCondition;
    }
 
    public static function or (...) {
        // some logic here
        return $orCondition;
    }
}
 
Cond::and($cond1, $cond2);

• Prevents unnecessary use of __call magic method (“->keyword_name_for_non_static_method()” works, but “public function keyword_name_for_non_static_method() {}” currently fails)

// Ugly, current code
class SomeClass {
    private $list = [];
 
    public function _list () {
        return $list;
    }
 
    public function __call ($func, $args) {
        if (method_exists($this, "_".$func)) {
            return call_user_func_array("_".$func, $args); // or some similar thing, if not underscores etc....
        }
        // some error handling here
    }
}
 
// How we could write it with the patch
class SomeClass {
    private $list = [];
 
    public function list () {
        return $list;
    }
}

Concretely this patch enables:

• all keywords for
  • method names
  • class constant names
  • declare directive names
• a limited set of keywords * for
  • class names
  • trait names
  • interface names
  • goto label names

* This includes all keywords except

• catch
• finally
• case
• default
• exit
• else
• elseif
• endif
• endwhile
• endfor
• endforeach
• enddeclare
• endswitch

It is necessary to exclude them due to limitations of bison/yacc grammar.

An example what is possible with this patch:

namespace Test {
    class List {
        const default = 0;
        public $case = array(array(self::default));
 
        public static function echo (List $instance) {
            var_dump($instance->case);
        }
 
        public function new (array $entry) {
            $this->case[] = $entry;
            return $this;
        }
    }
}
 
namespace {
    \Test\List::echo((new Test\List)->new(array(1)));
}

Currently when using array or callable as typehint, the old behaviour is preferred over comparing if it's a class/interface named array or callable. I'm not sure if we should just allow both in this special case.

This RFC should go into next PHP 5.x.

• The patch is against master
• Pull request is at https://github.com/php/php-src/pull/438

• Mailing List thread at http://markmail.org/message/7rn4mbwkbytqa3ig

• Initially the patch contained also some support for functions, namespaces and constants which was removed later due to some resulting syntactic inconsistencies