01-unless

unless — Ruby-style negated if

Inspiration: Ruby · Layer: front-end only (lexer + parser) · Commit: e2dfce0

What it is

unless is sugar for a negated if. It runs its body when the condition is false. Three forms are supported:

unless ($user->isBanned()) {                 // block form
    echo "welcome";
}

unless ($cache->has($key)) {                 // with else
    $value = compute();
} else {
    $value = $cache->get($key);
}

print "saved\n" unless $dryRun;              // statement modifier

unless (C) { S } is exactly equivalent to if (!C) { S }.

Why

It's the simplest possible language change — no new types, no runtime, no engine work — which made it the ideal warm-up for wiring up the whole build/patch/test loop. It also reads well for guard-style early conditions where if (!…) is noisy.

How it works

Entirely in the front-end; the compiler and runtime never learn about it.

1. Lexer (Zend/zend_language_scanner.l): a new keyword token T_UNLESS.
2. Parser (Zend/zend_language_parser.y): the unless rules desugar to the same AST that if produces — ZEND_AST_IF / ZEND_AST_IF_ELEM — with the condition wrapped in a boolean-NOT node (!C). Because it lowers to the existing if AST, there is zero new compiler or opcode surface.

unless is semi-reserved: it's added to reserved_non_modifiers, so it remains usable as a method or constant name ($obj->unless()), preserving backward compatibility.

Caveats

• None of note — it desugars to if, so semantics, scoping, and short-circuiting are identical.

Tests

• smoke.sh — smoke tests (block, else, modifier, semi-reserved usage)
• tests/unless.phpt, tests/unless_comprehensive.phpt — in-tree regression tests