Fix GH-25107: Preserve foreach iterators on array_unshift

NEWS

@@ -271,6 +271,8 @@ PHP                                                                        NEWS
     properties). (Lazizbek Ergashev)
 
 - Standard:
+  . Fixed bug GH-25107 (array_unshift() skips elements during foreach by
+    reference when the array contains holes). (JoaoMarcos44)
   . Fixed memory leaks in checkdnsrr() and dns_check_record() on Windows.
     (Ilia Alshanetsky)
   . Fixed __unserialize() and __wakeup() being called for objects with a missing

ext/standard/array.c

@@ -3826,7 +3826,25 @@ PHP_FUNCTION(array_unshift)
 	} ZEND_HASH_FOREACH_END();
 
 	if (UNEXPECTED(HT_HAS_ITERATORS(Z_ARRVAL_P(stack)))) {
-		zend_hash_iterators_advance(Z_ARRVAL_P(stack), argc);
+		HashTable *ht = Z_ARRVAL_P(stack);
+
+		if (!HT_IS_WITHOUT_HOLES(ht)) {
+			uint32_t iter_pos = zend_hash_iterators_lower_pos(ht, 0);
+			uint32_t compacted_pos = 0;
+			size_t element_size = ZEND_HASH_ELEMENT_SIZE(ht);
+
+			for (uint32_t idx = 0; idx < ht->nNumUsed; idx++) {
+				if (idx == iter_pos) {
+					zend_hash_iterators_update(ht, idx, compacted_pos);
+					iter_pos = zend_hash_iterators_lower_pos(ht, idx + 1);
+				}
+				if (Z_TYPE_P(ZEND_HASH_ELEMENT_EX(ht, idx, element_size)) != IS_UNDEF) {
+					compacted_pos++;
+				}
+			}
+			zend_hash_iterators_update(ht, ht->nNumUsed, compacted_pos);
+		}
+		zend_hash_iterators_advance(ht, argc);
 		HT_SET_ITERATORS_COUNT(&new_hash, HT_ITERATORS_COUNT(Z_ARRVAL_P(stack)));
 		HT_SET_ITERATORS_COUNT(Z_ARRVAL_P(stack), 0);
 	}

ext/standard/tests/array/gh25107.phpt

@@ -0,0 +1,84 @@
+--TEST--
+GH-25107 (array_unshift() skips values during reference iteration)
+--FILE--
+<?php
+function single(bool $mixed, string $mode): void {
+    $a = $mixed
+        ? ['a' => 'a', 'b' => 'b', 'c' => 'c', 'd' => 'd', 'e' => 'e']
+        : ['a', 'b', 'c', 'd', 'e'];
+    if ($mode !== 'dense') {
+        unset($a[$mixed ? 'a' : 0]);
+    }
+    $seen = [];
+    foreach ($a as &$v) {
+        $seen[] = $v;
+        if ($mode === 'end' && $v === 'e') {
+            array_unshift($a, 'x');
+            $a[] = 'after';
+        } elseif ($mode !== 'end' && $v === 'b') {
+            if ($mode === 'next-hole') {
+                unset($a[$mixed ? 'c' : 2]);
+            }
+            if ($mode === 'zero') {
+                array_unshift($a);
+            } elseif ($mode === 'many') {
+                array_unshift($a, 'x', 'y', 'z');
+            } else {
+                array_unshift($a, 'x');
+            }
+        }
+    }
+    unset($v);
+    echo ($mixed ? 'mixed' : 'packed'), ' ', $mode, ' ', json_encode($seen), "\n";
+}
+
+function nested(bool $mixed, bool $samePosition): void {
+    $a = $mixed
+        ? ['a' => 'a', 'b' => 'b', 'c' => 'c', 'd' => 'd', 'e' => 'e', 'f' => 'f']
+        : ['a', 'b', 'c', 'd', 'e', 'f'];
+    unset($a[$mixed ? 'a' : 0], $a[$mixed ? 'd' : 3]);
+    $outerSeen = [];
+    $innerSeen = [];
+    foreach ($a as &$outer) {
+        $outerSeen[] = $outer;
+        if ($outer !== 'b') {
+            continue;
+        }
+        foreach ($a as &$inner) {
+            $innerSeen[] = $inner;
+            if ($inner === ($samePosition ? 'b' : 'c')) {
+                array_unshift($a, 'x', 'y');
+            }
+        }
+        unset($inner);
+    }
+    unset($outer);
+    echo ($mixed ? 'mixed' : 'packed'), ' ', ($samePosition ? 'same' : 'different'),
+        ' ', json_encode($outerSeen), ' ', json_encode($innerSeen), "\n";
+}
+
+foreach ([false, true] as $mixed) {
+    foreach (['dense', 'one', 'many', 'zero', 'next-hole', 'end'] as $mode) {
+        single($mixed, $mode);
+    }
+    nested($mixed, false);
+    nested($mixed, true);
+}
+?>
+--EXPECT--
+packed dense ["a","b","c","d","e"]
+packed one ["b","c","d","e"]
+packed many ["b","c","d","e"]
+packed zero ["b","c","d","e"]
+packed next-hole ["b","d","e"]
+packed end ["b","c","d","e","after"]
+packed different ["b","c","e","f"] ["b","c","e","f"]
+packed same ["b","c","e","f"] ["b","c","e","f"]
+mixed dense ["a","b","c","d","e"]
+mixed one ["b","c","d","e"]
+mixed many ["b","c","d","e"]
+mixed zero ["b","c","d","e"]
+mixed next-hole ["b","d","e"]
+mixed end ["b","c","d","e","after"]
+mixed different ["b","c","e","f"] ["b","c","e","f"]
+mixed same ["b","c","e","f"] ["b","c","e","f"]