Control Flow

Conditionals: if, elseif, else

Conditionals in RHP support standard boolean evaluations:

int $statusCode = 200;

if ($statusCode === 200) {
    print("Success: Request completed");
} elseif ($statusCode >= 400 && $statusCode < 500) {
    print("Client Error");
} else {
    print("Server Error");
}

Control Flow Normalization (elseif vs else if)

In RHP, chained conditionals are standardized strictly on the monolithic keyword elseif:

• Standard Monolithic Keyword: Always use elseif for secondary conditional branches.
• Prohibition of Two-Word else if: The separated two-word sequence else if is rejected at compile time to eliminate dangling-else ambiguities and ensure code formatting consistency.

// ✅ Valid:
if ($status === 'active') {
    $code = 1;
} elseif ($status === 'pending') {
    $code = 2;
} else {
    $code = 0;
}

// ❌ Rejected by compiler:
// if ($status === 'active') {
//     $code = 1;
// } else if ($status === 'pending') { // ParseError
//     $code = 2;
// }

When else if is encountered, the compiler halts with an explicit error:

SyntaxError: Use 'elseif' instead of 'else if'.

Pattern Matching with match Expressions

RHP supports first-class match expressions. Unlike switch, match returns a value, enforces strict === type checking, and does not require break statements:

int $roleId = 1;

string $roleTitle = match ($roleId) {
    1 => 'Administrator',
    2 => 'Editor',
    3 => 'Subscriber',
    default => 'Guest',
};

print("User Role: " . $roleTitle);

Iteration: foreach Over Subtyped Collections

The foreach construct iterates smoothly over all RHP collection subtypes (list, dict, set, hashMap).

For dictionaries (Arr::dict), foreach drives a zero-allocation streaming iterator (ActiveIterator::Dict) that accesses entries directly via internal index offsets without allocating temporary key/value arrays, strictly maintaining insertion order:

// Iterating over a list (sequential 0-based index)
list $users = Arr::list(['Alice', 'Bob', 'Charlie']);
foreach ($users as $index => $name) {
    Sys::print("[{}]: {}", $index, $name);
}

// Iterating over an ordered dictionary (strict insertion order preserved)
dict $meta = Arr::dict([
    'region'  => 'us-east-1',
    'active'  => true,
    'cluster' => 'k8s-prod',
]);
foreach ($meta as $key => $value) {
    Sys::print("{} => {}", $key, (string)$value);
}

Loops: for and while

// Standard for loop
for (int $i = 0; $i < 5; $i++) {
    if ($i === 2) continue;
    print("Step: " . (string)$i);
}

// While loop
int $attempts = 3;
while ($attempts > 0) {
    $attempts--;
}