Fixed bug #69889

nikic · nikic · commit 9fa70dbd29f9 · 2015-06-20T15:09:58.000+02:00
There is one case that requires further discussion:

$foo = "test";
var_dump($foo[0.0] ?? "default");
var_dump(isset($foo[0.0]) ? $foo[0.0] : "default");

Here the former will currently return "t", while the latter also
returns "t" and additionally throws a notice.

I think we need to revisit the behavior of invalid types for string
offset access in PHP 7, as currently there is some mismatch between
what isset() does and what the access itself supports.
diff --git a/NEWS b/NEWS
@@ -20,6 +20,8 @@ PHP                                                                        NEWS
     7/8/8.1/10 as "Business"). (Christian Wenz)
   . Fixes bug #69835 (phpinfo() does not report many Windows SKUs).
     (Christian Wenz)
+  . Fixed bug #69889 (Null coalesce operator doesn't work for string offsets).
+    (Nikita)
 
 - DOM:
   . Fixed bug #69846 (Segmenation fault (access violation) when iterating over
diff --git a/Zend/tests/bug69889.phpt b/Zend/tests/bug69889.phpt
@@ -0,0 +1,22 @@
+--TEST--
+Bug #69889: Null coalesce operator doesn't work for string offsets
+--FILE--
+<?php
+
+$foo = "test";
+var_dump($foo[0] ?? "default");
+
+var_dump($foo[5] ?? "default");
+var_dump(isset($foo[5]) ? $foo[5] : "default");
+
+var_dump($foo["str"] ?? "default");
+var_dump(isset($foo["str"]) ? $foo["str"] : "default");
+
+?>
+--EXPECT--
+string(1) "t"
+string(7) "default"
+string(7) "default"
+string(7) "default"
+string(7) "default"
+
diff --git a/Zend/zend_execute.c b/Zend/zend_execute.c
@@ -1781,9 +1781,11 @@ static zend_always_inline void zend_fetch_dimension_address_read(zval *result, z
 					if (IS_LONG == is_numeric_string(Z_STRVAL_P(dim), Z_STRLEN_P(dim), NULL, NULL, -1)) {
 						break;
 					}
-					if (type != BP_VAR_IS) {
-						zend_error(E_WARNING, "Illegal string offset '%s'", Z_STRVAL_P(dim));
+					if (type == BP_VAR_IS) {
+						ZVAL_NULL(result);
+						return;
 					}
+					zend_error(E_WARNING, "Illegal string offset '%s'", Z_STRVAL_P(dim));
 					break;
 				case IS_DOUBLE:
 				case IS_NULL:
@@ -1809,8 +1811,10 @@ static zend_always_inline void zend_fetch_dimension_address_read(zval *result, z
 		if (UNEXPECTED(offset < 0) || UNEXPECTED(Z_STRLEN_P(container) <= (size_t)offset)) {
 			if (type != BP_VAR_IS) {
 				zend_error(E_NOTICE, "Uninitialized string offset: %pd", offset);
+				ZVAL_EMPTY_STRING(result);
+			} else {
+				ZVAL_NULL(result);
 			}
-			ZVAL_EMPTY_STRING(result);
 		} else {
 			zend_uchar c = (zend_uchar)Z_STRVAL_P(container)[offset];
 
