Implement namespace extraction utilities for visibility checks

Add helper functions to extract and compare namespaces at runtime:

* zend_extract_namespace() - Extracts "Foo\Bar" from "Foo\Bar\ClassName"
* zend_get_class_namespace() - Gets namespace from class entry name
* zend_get_caller_namespace() - Determines namespace of executing code
  - From methods: uses class namespace
  - From functions: uses op_array->namespace_name
  - From top-level: uses op_array->namespace_name

These utilities will be used by visibility checking code to enforce
namespace-scoped access rules.

Important: For trait methods, scope is the class that uses the trait,
not the trait itself. This means private(namespace) in traits is checked
against the receiver's namespace, which is the desired behavior.

Author: withinboredom

Zend/zend_API.c

@@ -5299,3 +5299,62 @@ ZEND_API zend_result zend_get_default_from_internal_arg_info(
 #endif
 	return get_default_via_ast(default_value_zval, default_value);
 }
+
+/* Namespace extraction helpers for private(namespace) visibility */
+
+/* Extract namespace from a fully-qualified name
+ * Examples:
+ *   "Foo\\Bar\\ClassName" -> "Foo\\Bar"
+ *   "ClassName" -> "" (empty string for global namespace)
+ */
+ZEND_API zend_string* zend_extract_namespace(const zend_string *name)
+{
+	const char *class_name = ZSTR_VAL(name);
+	const char *last_separator = zend_memrchr(class_name, '\\', ZSTR_LEN(name));
+
+	if (last_separator == NULL) {
+		/* No namespace separator found: global namespace */
+		return ZSTR_EMPTY_ALLOC();
+	}
+
+	/* Extract namespace part (everything before the last backslash) */
+	size_t namespace_len = last_separator - class_name;
+	return zend_string_init(class_name, namespace_len, 0);
+}
+
+/* Get namespace from a class entry */
+ZEND_API zend_string* zend_get_class_namespace(const zend_class_entry *ce)
+{
+	return zend_extract_namespace(ce->name);
+}
+
+/* Get the namespace of the currently executing code */
+ZEND_API zend_string* zend_get_caller_namespace(void)
+{
+	zend_execute_data *ex = EG(current_execute_data);
+
+	if (!ex || !ex->func) {
+		/* No execution context - global namespace */
+		return ZSTR_EMPTY_ALLOC();
+	}
+
+	/* Case 1: Called from a method: use the class namespace
+	 * For trait methods, scope is the class that uses the trait,
+	 * not the trait itself. This is the desired behavior. */
+	if (ex->func->common.scope) {
+		return zend_get_class_namespace(ex->func->common.scope);
+	}
+
+	/* Case 2: Called from a user function or top-level code */
+	if (ex->func->type == ZEND_USER_FUNCTION) {
+		zend_op_array *op_array = &ex->func->op_array;
+
+		/* Use the namespace_name field we added to op_array */
+		if (op_array->namespace_name) {
+			return op_array->namespace_name;
+		}
+	}
+
+	/* Case 3: Internal function or global namespace */
+	return ZSTR_EMPTY_ALLOC();
+}

Zend/zend_API.h

@@ -927,6 +927,11 @@ ZEND_API bool zend_is_countable(const zval *countable);
 ZEND_API zend_result zend_get_default_from_internal_arg_info(
 		zval *default_value_zval, const zend_internal_arg_info *arg_info);
 
+/* Namespace extraction helpers for private(namespace) visibility */
+ZEND_API zend_string* zend_extract_namespace(const zend_string *name);
+ZEND_API zend_string* zend_get_class_namespace(const zend_class_entry *ce);
+ZEND_API zend_string* zend_get_caller_namespace(void);
+
 END_EXTERN_C()
 
 #if ZEND_DEBUG