PHP Engine Attributes

Tier 2Complete

PHP Core attributes such as #[\Deprecated], #[\Override], #[\NoDiscard], and #[\DelayedTargetValidation] emit as ordinary PHP attributes. Tyhp type-checks them at compile time. The attribute classes stay version-gated in tyhpdef/php; some checks still run when output.phpVersion is below the introducing minor. See PHP Version Gating.

tyhp --explain TYHP#### prints the long-form text for each code below.

#[\Deprecated]

#[\Deprecated] marks a declaration as deprecated. Using that symbol warns TYHP4500. The binder treats the attribute the same way as the tyhpdef deprecated keyword — both set deprecation on the symbol, and both produce this one warning.

When $message is a string literal, it is appended to the diagnostic after a colon ({0} is the name, {1} is : plus the message). Omit $message and the warning stays the one-argument form `{0}` is deprecated. $since is not part of the short message.

Tyhp warns even when output.phpVersion is below 8.4. PHP’s runtime E_USER_DEPRECATED is a no-op on older minors; the compile-time warning still fires.

<?tyhp

#[\Deprecated('use bar()')]
function foo(): void {}

foo();  // WARNING TYHP4500: `foo` is deprecated: use bar()

On a tyhpdef, deprecated function baz(); is the same warning without an attribute. See The deprecated and obsolete Keywords.

#[\Override]

#[\Override] marks a method — and, when output.phpVersion is 8.5 or later, a property — as intended to replace a parent or interface member.

• If no same-name non-private ancestor or interface member exists, that is TYHP4129.
• On a target below 8.5, #[\Override] on a property is a target mismatch (TYHP4127).
• On __construct, TYHP4339 always — constructors are exempt from override semantics, even when a parent constructor exists.

Trait method bodies are not checked here; PHP applies the attribute on the composing class.

<?tyhp

class Base {
    public int $x = 0;

    public function label(): string {
        return 'base';
    }
}

class Child extends Base {
    #[\Override]
    public function label(): string {
        return 'child';
    }

    // Legal when output.phpVersion is 8.5 or later and Base has $x:
    #[\Override]
    public int $x = 1;

    // ERROR TYHP4339 at every phpVersion:
    // #[\Override]
    // public function __construct(): void {}
}

A method or property that is marked but does not override uses TYHP4129, not TYHP4339.

#[\NoDiscard]

#[\NoDiscard] marks a function or method whose return value should be used. A discarded call (an expression statement, or a non-final for list item) warns TYHP4165. When $message is a string literal, it is appended after a colon, the same way as #[\Deprecated].

Use the return (assignment, argument, condition, and so on), or discard it on purpose with (void):

<?tyhp

#[\NoDiscard('check the status')]
function save(): int {
    return 1;
}

function run(): void {
    save();               // WARNING TYHP4165, including ": check the status"
    (void)save();         // OK
    int $n = save();      // OK
    $_ = save();          // OK — assignment is a use
}

The warning comes from the invoked declaration:

• Calling through an interface or abstract method does not warn, even if that declaration is marked.
• An override does not inherit the warning unless it is itself marked.
• A trait-imported method keeps the attribute (PHP copies it onto the using class).

Tyhp reports this even when output.phpVersion is below 8.5. (void) is native PHP on 8.5 or later; below 8.5 the emitter omits the cast and still treats it as an intentional discard.

#[\DelayedTargetValidation]

On PHP 8.5, #[\DelayedTargetValidation] on a declaration defers target (TARGET_*) errors for internal (Core) attributes on that same declaration until ReflectionAttribute::newInstance(). Tyhp’s compile-time analogue: when output.phpVersion is 8.5 or later and this attribute is on the declaration, TYHP4127 is skipped for Core attributes on that declaration.

Functional checks still run. #[\Override] that does not override is still TYHP4129. Unused #[\NoDiscard] returns are still TYHP4165. #[\Override] on __construct is still TYHP4339.

Below 8.5 the skip is ignored — target mismatches are still reported.

<?tyhp

class Base {
    public int $x = 0;
}

class Child extends Base {
    // On 8.5, `#[\Override]` on a property is already a legal target, so there is nothing
    // for `#[\DelayedTargetValidation]` to skip here. Base has $x, so this is not TYHP4129 either.
    #[\DelayedTargetValidation]
    #[\Override]
    public int $x = 1;
}

class Orphan {
    // Still TYHP4129: `#[\DelayedTargetValidation]` only skips the TARGET_* check, not the
    // override check. Orphan has no parent, so there is no $y to override.
    #[\DelayedTargetValidation]
    #[\Override]
    public int $y = 1;
}

Userland attributes are still target-checked. Only PHP Core engine attributes on that declaration skip TYHP4127.

#[\SensitiveParameter]

#[\SensitiveParameter] on a parameter has no use-site diagnostic. In the debugger, marked arguments stay wrapped as \SensitiveParameterValue. See CLI: Xdebug Proxy.

Diagnostics

See the Diagnostic Code Reference for the compiler’s short messages.

Common mistakes