fix bug #75173 incorrect behavior of AppendIterator::append in foreach loop

NEWS

@@ -33,6 +33,10 @@ PHP                                                                        NEWS
   . Fixed bug #74631 (PDO_PCO with PHP-FPM: OCI environment initialized
     before PHP-FPM sets it up). (Ingmar Runge)
 
+- SPL:
+  . Fixed bug #75173 (incorrect behavior of AppendIterator::append in foreach loop).
+    (jhdxr)
+
 - Standard:
   . Fixed bug #75097 (gethostname fails if your host name is 64 chars long). (Andrea)
 

ext/spl/spl_iterators.c

@@ -3384,7 +3384,7 @@ SPL_METHOD(AppendIterator, append)
 	if (zend_parse_parameters_ex(ZEND_PARSE_PARAMS_QUIET, ZEND_NUM_ARGS(), "O", &it, zend_ce_iterator) == FAILURE) {
 		return;
 	}
-	if (intern->u.append.iterator->funcs->valid(intern->u.append.iterator) == SUCCESS) {
+	if (intern->u.append.iterator->funcs->valid(intern->u.append.iterator) == SUCCESS && spl_dual_it_valid(intern) != SUCCESS) {
 		spl_array_iterator_append(&intern->u.append.zarrayit, it);
 		intern->u.append.iterator->funcs->move_forward(intern->u.append.iterator);
 	}else{

ext/spl/tests/bug75173.phpt

@@ -0,0 +1,18 @@
+--TEST--
+Bug #75173 incorrect behavior of AppendIterator::append in foreach loop
+--FILE--
+<?php
+
+$it = new \AppendIterator();
+$it->append(new ArrayIterator(['foo']));
+
+foreach ($it as $item) {
+    var_dump($item);
+    
+    if ('foo' === $item) {
+        $it->append(new ArrayIterator(['bar']));
+    }
+}
+--EXPECT--
+string(3) "foo"
+string(3) "bar"