extphprs · kakserpom · Jan 26, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,22 +1,33 @@
 # Changelog
 
+## Unreleased
+
+### BREAKING CHANGES
+
+- *(macro)* [**breaking**] Functions and methods without an explicit return type now declare `void` as their PHP return type instead of having no return type (implicit `mixed`). This improves type safety but may cause errors if your function actually returns a value without declaring it. Magic methods `__destruct` and `__clone` are excluded as PHP forbids return types on them. See [migration guide](guide/src/migration-guides/v0.16.md).
+
+### Added
+
+- *(interface)* `#[php_impl_interface]` macro for implementing PHP interfaces via Rust traits [[#590](https://github.com/davidcole1340/ext-php-rs/issues/590)]
+
 ## [0.15.4](https://github.com/extphprs/ext-php-rs/compare/ext-php-rs-v0.15.3...ext-php-rs-v0.15.4) - 2026-01-26
 
 ### Added
-- *(array)* Entry API (Issue #525) ([#611](https://github.com/extphprs/ext-php-rs/pull/611)) (by @kakserpom) [[#525](https://github.com/davidcole1340/ext-php-rs/issues/525)] [[#611](https://github.com/davidcole1340/ext-php-rs/issues/611)] 
-- *(class)* Readonly and final classes ([#639](https://github.com/extphprs/ext-php-rs/pull/639)) (by @kakserpom) [[#639](https://github.com/davidcole1340/ext-php-rs/issues/639)] 
-- *(core)* Add observer API ([#650](https://github.com/extphprs/ext-php-rs/pull/650)) (by @ptondereau) [[#650](https://github.com/davidcole1340/ext-php-rs/issues/650)] 
-- *(object)* Lazy ghost and Lazy Proxy ([#636](https://github.com/extphprs/ext-php-rs/pull/636)) (by @kakserpom) [[#636](https://github.com/davidcole1340/ext-php-rs/issues/636)] 
-- *(string)* Smartstring support ([#643](https://github.com/extphprs/ext-php-rs/pull/643)) (by @kakserpom) [[#643](https://github.com/davidcole1340/ext-php-rs/issues/643)] 
+- *(array)* Entry API (Issue #525) ([#611](https://github.com/extphprs/ext-php-rs/pull/611)) (by @kakserpom) [[#525](https://github.com/davidcole1340/ext-php-rs/issues/525)] [[#611](https://github.com/davidcole1340/ext-php-rs/issues/611)]
+- *(class)* Readonly and final classes ([#639](https://github.com/extphprs/ext-php-rs/pull/639)) (by @kakserpom) [[#639](https://github.com/davidcole1340/ext-php-rs/issues/639)]
+- *(core)* Add observer API ([#650](https://github.com/extphprs/ext-php-rs/pull/650)) (by @ptondereau) [[#650](https://github.com/davidcole1340/ext-php-rs/issues/650)]
+- *(object)* Lazy ghost and Lazy Proxy ([#636](https://github.com/extphprs/ext-php-rs/pull/636)) (by @kakserpom) [[#636](https://github.com/davidcole1340/ext-php-rs/issues/636)]
+- *(string)* Smartstring support ([#643](https://github.com/extphprs/ext-php-rs/pull/643)) (by @kakserpom) [[#643](https://github.com/davidcole1340/ext-php-rs/issues/643)]
 
 ### Fixed
-- *(cargo-php)* Use runtime feature for cargo-php to avoid dynamic linking on musl ([#645](https://github.com/extphprs/ext-php-rs/pull/645)) (by @ptondereau) [[#645](https://github.com/davidcole1340/ext-php-rs/issues/645)] 
-- *(clippy)* V1.93.0 errors ([#648](https://github.com/extphprs/ext-php-rs/pull/648)) (by @ptondereau) [[#648](https://github.com/davidcole1340/ext-php-rs/issues/648)] 
-- *(deps)* Bump parking_lot required version to 0.12.3 (by @TobiasBengtsson) [[#640](https://github.com/davidcole1340/ext-php-rs/issues/640)] 
-- *(doc)* Update mdbook config ([#651](https://github.com/extphprs/ext-php-rs/pull/651)) (by @ptondereau) [[#651](https://github.com/davidcole1340/ext-php-rs/issues/651)] 
-- *(macro)* Refactor allowed and forbidden keywords to match PHP parser ([#647](https://github.com/extphprs/ext-php-rs/pull/647)) (by @ptondereau) [[#647](https://github.com/davidcole1340/ext-php-rs/issues/647)] 
-- *(windows)* Add fallback for 404 errors in windows build ([#649](https://github.com/extphprs/ext-php-rs/pull/649)) (by @ptondereau) [[#649](https://github.com/davidcole1340/ext-php-rs/issues/649)] 
-- Handle PHP mocks and subclasses of Rust-backed classes ([#653](https://github.com/extphprs/ext-php-rs/pull/653)) (by @ptondereau) [[#653](https://github.com/davidcole1340/ext-php-rs/issues/653)] 
+- *(cargo-php)* Use runtime feature for cargo-php to avoid dynamic linking on musl ([#645](https://github.com/extphprs/ext-php-rs/pull/645)) (by @ptondereau) [[#645](https://github.com/davidcole1340/ext-php-rs/issues/645)]
+- *(clippy)* V1.93.0 errors ([#648](https://github.com/extphprs/ext-php-rs/pull/648)) (by @ptondereau) [[#648](https://github.com/davidcole1340/ext-php-rs/issues/648)]
+- *(deps)* Bump parking_lot required version to 0.12.3 (by @TobiasBengtsson) [[#640](https://github.com/davidcole1340/ext-php-rs/issues/640)]
+- *(doc)* Update mdbook config ([#651](https://github.com/extphprs/ext-php-rs/pull/651)) (by @ptondereau) [[#651](https://github.com/davidcole1340/ext-php-rs/issues/651)]
+- *(macro)* Refactor allowed and forbidden keywords to match PHP parser ([#647](https://github.com/extphprs/ext-php-rs/pull/647)) (by @ptondereau) [[#647](https://github.com/davidcole1340/ext-php-rs/issues/647)]
+- *(windows)* Add fallback for 404 errors in windows build ([#649](https://github.com/extphprs/ext-php-rs/pull/649)) (by @ptondereau) [[#649](https://github.com/davidcole1340/ext-php-rs/issues/649)]
+- Handle PHP mocks and subclasses of Rust-backed classes ([#653](https://github.com/extphprs/ext-php-rs/pull/653)) (by @ptondereau) [[#653](https://github.com/davidcole1340/ext-php-rs/issues/653)]
+
 ## [0.15.3](https://github.com/extphprs/ext-php-rs/compare/ext-php-rs-v0.15.2...ext-php-rs-v0.15.3) - 2025-12-28
 
 ### Added

diff --git a/Cargo.toml b/Cargo.toml
@@ -23,6 +23,7 @@ cfg-if = "1.0"
 once_cell = "1.21"
 anyhow = { version = "1", optional = true }
 smartstring = { version = "1", optional = true }
+inventory = "0.3"
 ext-php-rs-derive = { version = "=0.11.7", path = "./crates/macros" }
 
 [dev-dependencies]

diff --git a/crates/macros/src/class.rs b/crates/macros/src/class.rs
@@ -343,6 +343,24 @@ fn generate_registered_class_impl(
                 ::ext_php_rs::internal::class::PhpClassImplCollector::<Self>::default().get_constants()
             }
 
+            #[inline]
+            fn interface_implementations() -> ::std::vec::Vec<::ext_php_rs::class::ClassEntryInfo> {
+                let my_type_id = ::std::any::TypeId::of::<Self>();
+                ::ext_php_rs::inventory::iter::<::ext_php_rs::internal::class::InterfaceRegistration>()
+                    .filter(|reg| reg.class_type_id == my_type_id)
+                    .map(|reg| (reg.interface_getter)())
+                    .collect()
+            }
+
+            #[inline]
+            fn interface_method_implementations() -> ::std::vec::Vec<(
+                ::ext_php_rs::builders::FunctionBuilder<'static>,
+                ::ext_php_rs::flags::MethodFlags,
+            )> {
+                use ::ext_php_rs::internal::class::InterfaceMethodsProvider;
+                ::ext_php_rs::internal::class::PhpClassImplCollector::<Self>::default().get_interface_methods()
+            }
+
             #default_init_impl
         }
     }

diff --git a/crates/macros/src/function.rs b/crates/macros/src/function.rs
@@ -317,46 +317,59 @@ impl<'a> Function<'a> {
         }
     }
 
-    fn build_returns(&self, call_type: Option<&CallType>) -> Option<TokenStream> {
-        self.output.cloned().map(|mut output| {
-            output.drop_lifetimes();
-
-            // If returning &Self or &mut Self from a method, use the class type
-            // for return type information since we return `this` (ZendClassObject)
-            if returns_self_ref(self.output)
-                && let Some(CallType::Method { class, .. }) = call_type
+    fn build_returns(&self, call_type: Option<&CallType>) -> TokenStream {
+        let Some(output) = self.output.cloned() else {
+            // PHP magic methods __destruct and __clone cannot have return types
+            // (only applies to class methods, not standalone functions)
+            if matches!(call_type, Some(CallType::Method { .. }))
+                && (self.name == "__destruct" || self.name == "__clone")
             {
-                return quote! {
-                    .returns(
-                        <&mut ::ext_php_rs::types::ZendClassObject<#class> as ::ext_php_rs::convert::IntoZval>::TYPE,
-                        false,
-                        <&mut ::ext_php_rs::types::ZendClassObject<#class> as ::ext_php_rs::convert::IntoZval>::NULLABLE,
-                    )
-                };
+                return quote! {};
             }
+            // No return type means void in PHP
+            return quote! {
+                .returns(::ext_php_rs::flags::DataType::Void, false, false)
+            };
+        };
 
-            // If returning Self (new instance) from a method, replace Self with
-            // the actual class type since Self won't resolve in generated code
-            if returns_self(self.output)
-                && let Some(CallType::Method { class, .. }) = call_type
-            {
-                return quote! {
-                    .returns(
-                        <#class as ::ext_php_rs::convert::IntoZval>::TYPE,
-                        false,
-                        <#class as ::ext_php_rs::convert::IntoZval>::NULLABLE,
-                    )
-                };
-            }
+        let mut output = output;
+        output.drop_lifetimes();
 
-            quote! {
+        // If returning &Self or &mut Self from a method, use the class type
+        // for return type information since we return `this` (ZendClassObject)
+        if returns_self_ref(self.output)
+            && let Some(CallType::Method { class, .. }) = call_type
+        {
+            return quote! {
                 .returns(
-                    <#output as ::ext_php_rs::convert::IntoZval>::TYPE,
+                    <&mut ::ext_php_rs::types::ZendClassObject<#class> as ::ext_php_rs::convert::IntoZval>::TYPE,
                     false,
-                    <#output as ::ext_php_rs::convert::IntoZval>::NULLABLE,
+                    <&mut ::ext_php_rs::types::ZendClassObject<#class> as ::ext_php_rs::convert::IntoZval>::NULLABLE,
                 )
-            }
-        })
+            };
+        }
+
+        // If returning Self (new instance) from a method, replace Self with
+        // the actual class type since Self won't resolve in generated code
+        if returns_self(self.output)
+            && let Some(CallType::Method { class, .. }) = call_type
+        {
+            return quote! {
+                .returns(
+                    <#class as ::ext_php_rs::convert::IntoZval>::TYPE,
+                    false,
+                    <#class as ::ext_php_rs::convert::IntoZval>::NULLABLE,
+                )
+            };
+        }
+
+        quote! {
+            .returns(
+                <#output as ::ext_php_rs::convert::IntoZval>::TYPE,
+                false,
+                <#output as ::ext_php_rs::convert::IntoZval>::NULLABLE,
+            )
+        }
     }
 
     fn build_result(