A brief discussion of PHP source code twenty-nine: About inheritance of interfaces

This article mainly introduces the twenty-nine about PHP source code: Regarding the inheritance of interfaces, it has a certain reference value. Now I share it with you. Friends in need can refer to it.

A brief talk about PHP Source Code Twenty-Nine: About Interface Inheritance

I have seen the inheritance of classes in PHP source code before. Today we will take a look at how interface inheritance in PHP is implemented.
Similarly, we start from the CachingIterator class to find the inherited implementation of the interface.
CachingIterator extends IteratorIterator implements OuterIterator, Traversable, Iterator, ArrayAccess, Countable

  /* ArrayAccess接口的继承实现 */REGISTER_SPL_IMPLEMENTS(CachingIterator, ArrayAccess); //    ext/spl/spl_functions.h 41行#define REGISTER_SPL_IMPLEMENTS(class_name, interface_name) \
zend_class_implements(spl_ce_ ## class_name TSRMLS_CC, 1, spl_ce_ ## interface_name); //zend/zend_API.c 2218行ZEND_API void zend_class_implements(zend_class_entry *class_entry TSRMLS_DC, int num_interfaces, ...) /* {{{ */{
zend_class_entry *interface_entry;
va_list interface_list;
va_start(interface_list, num_interfaces); while (num_interfaces--) {
interface_entry = va_arg(interface_list, zend_class_entry *);
zend_do_implement_interface(class_entry, interface_entry TSRMLS_CC);
} va_end(interface_list);}/* }}} */ 
 
 //zend/zend_complie.c 2887行ZEND_API void zend_do_implement_interface(zend_class_entry *ce, zend_class_entry *iface TSRMLS_DC) /* {{{ */{
zend_uint i, ignore = 0;
zend_uint current_iface_num = ce->num_interfaces;
zend_uint parent_iface_num  = ce->parent ? ce->parent->num_interfaces : 0; for (i = 0; i < ce->num_interfaces; i++) {
if (ce->interfaces[i] == NULL) {
memmove(ce->interfaces + i, ce->interfaces + i + 1, sizeof(zend_class_entry*) * (--ce->num_interfaces - i));
i--;
} else if (ce->interfaces[i] == iface) {/* 已存在此接口 */
if (i < parent_iface_num) {
ignore = 1;
} else {
zend_error(E_COMPILE_ERROR, "Class %s cannot implement previously implemented interface %s", ce->name, iface->name);
}
}
}
if (!ignore) {
if (ce->num_interfaces >= current_iface_num) {
if (ce->type == ZEND_INTERNAL_CLASS) {
ce->interfaces = (zend_class_entry **) realloc(ce->interfaces, sizeof(zend_class_entry *) * (++current_iface_num));
} else {
ce->interfaces = (zend_class_entry **) erealloc(ce->interfaces, sizeof(zend_class_entry *) * (++current_iface_num));
}
}
ce->interfaces[ce->num_interfaces++] = iface;//接口数加1，将接口加入接口列表中 /* 合并接口中的常量列表和方法列表 */
zend_hash_merge_ex(&ce->constants_table, &iface->constants_table, (copy_ctor_func_t) zval_add_ref, sizeof(zval *), (merge_checker_func_t) do_inherit_constant_check, iface);
zend_hash_merge_ex(&ce->function_table, &iface->function_table, (copy_ctor_func_t) do_inherit_method, sizeof(zend_function), (merge_checker_func_t) do_inherit_method_check, ce); 
do_implement_interface(ce, iface TSRMLS_CC);
zend_do_inherit_interfaces(ce, iface TSRMLS_CC);
}}

From the constant list and method list operations in the merged interface of the zend_do_implement_interface function, we can guess that this may be because there cannot be variables in the interface. One of the reasons for constants
In the process of interface inheritance, there is a judgment operation on whether the same interface exists in the interface of the current class. If the same interface already exists, this interface will not be inherited.
The php code is as follows:

<?phpinterface FooInterface {
public function method1();} class Base implements FooInterface {
public function method1() {
echo &#39;ss&#39;;
}} class Foo extends Base implements FooInterface { } $foo = new Foo();$foo->method1();

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