Keywords Reference

Reserved Keywords

The following identifiers are reserved language keywords and cannot be used as standalone function or class names:

abstract    as          async       break       case        catch
class       const       continue    default     defer       do
else        elseif      enum        extends     final       finally
fn          for         foreach     function    if          implements
interface   import      macro       match       namespace   new
private     protected   public      readonly    return      singleton
static      switch      throw       trait       try         use
while       yield

Keyword-as-Method-Name Resolution

Keywords such as match, default, from, for, class, new, static, and clone are reserved as strict language keywords primarily at statement-start contexts:

• Object Accessor Resolution: When any keyword follows an object accessor (->, ?->) or scope resolution operator (::), the parser lookahead stage contextually re-classifies the token as an identifier method or property name.
• Static Facade Disambiguation: When an operation requires explicit disambiguation, RHP provides the built-in Glob static facade (e.g. Glob::getClass($obj), Glob::match($pattern, $subject)).

// Valid: Keywords invoked as method or property accessors
$obj->match();
$obj->default();
$obj->from();
$obj->for();
$obj->class;
$obj->new();
$obj->static();
$obj->clone();

// Disambiguation via static facade
Glob::getClass($obj);
Glob::match('/^[a-z]+$/', $input);

Type Keywords

The following primitive and collection subtype keywords are reserved for type annotations:

int         float       string      bool        void        mixed
array       list        dict        set         hashmap     map
callable    iterable    object      never       null

Strict Case-Sensitivity & Forbidden Aliases

RHP enforces strict case-sensitivity for literals and primitive types to maintain compiler performance and eliminate ambiguity:

• Strictly Valid Literals (Lowercase Only): true, false, null. Capitalized variants (TRUE, FALSE, NULL) are rejected as unknown identifiers.
• Strictly Valid Primitives (Lowercase Only): string, bool, int, float.
• Rejected Aliases: Capitalized variants (String, Boolean, Integer) and legacy PHP aliases (boolean, integer) are rejected by the type checker.

// Valid: strictly lowercase primitives
int $count = 42;
string $name = "Alice";
bool $flag = true;
$emptyVal = null;

// Rejected by type checker:
// String $a;   // Error: Invalid primitive type 'String'
// Boolean $b;  // Error: Invalid primitive type 'Boolean'
// integer $c;  // Error: Invalid primitive type 'integer'

Collection & Type Boundary Rules

Default Numeric Storage

[!IMPORTANT] Both int and float default to i32 (32-bit) storage. Neither maps to f64 by default. Use Int::i64(...) or Float::f64(...) for wider precision.

Int and Float — Facade Identifiers (Not Type Keywords)

Int and Float (capitalized) are static facade class identifiers, not type keywords. They cannot be used as type annotations and cannot be instantiated with new:

// ✅ Valid — lowercase type keyword annotations
function calc(int $a, float $b): float { ... }

// ✅ Valid — capitalized facade static method calls
$id = Int::i64(9223372036854775807);
$formatted = Float::f64(3.14)->toDecimal(2);

// ❌ ParseError — Int/Float cannot be used as type annotations
function broken(Int $a): Float { ... }

// ❌ Fatal Error — Int/Float cannot be instantiated
$x = new Int();

Special Identifiers & Superglobals

Note on Superglobals in RHP: Direct use of $_GET, $_POST, $_SESSION, and $_COOKIE is deprecated. RHP provides modern, type-safe static facades (Request, Session, and Cookie). The rhp run lint command reports deprecated-superglobal warnings when legacy superglobals are used.

Module & Native Import Keywords

Explicitly Disallowed Keywords: await

RHP deliberately rejects the await keyword to eliminate function coloring across codebases.