Fix str_decrement() on "1"

Closes GH-12339

NEWS

@@ -25,6 +25,9 @@ PHP                                                                        NEWS
 - SimpleXML:
   . Apply iterator fixes only on master. (nielsdos)
 
+- Standard:
+  . Fixed str_decrement() on "1". (ilutov)
+
 - XSL:
   . Fix type error on XSLTProcessor::transformToDoc return value with
     SimpleXML. (nielsdos)

ext/standard/string.c

@@ -1289,7 +1289,7 @@ PHP_FUNCTION(str_decrement)
 		}
 	} while (carry && position-- > 0);
 
-	if (UNEXPECTED(carry || ZSTR_VAL(decremented)[0] == '0')) {
+	if (UNEXPECTED(carry || (ZSTR_VAL(decremented)[0] == '0' && ZSTR_LEN(decremented) > 1))) {
 		if (ZSTR_LEN(decremented) == 1) {
 			zend_string_release_ex(decremented, /* persistent */ false);
 			zend_argument_value_error(1, "\"%s\" is out of decrement range", ZSTR_VAL(str));

ext/standard/tests/strings/str_decrement_basic.phpt

@@ -28,6 +28,7 @@ $strictlyAlphaNumeric = [
     "d",
     "D",
     "4",
+    "1",
 ];
 
 foreach ($strictlyAlphaNumeric as $s) {
@@ -77,3 +78,5 @@ string(1) "C"
 string(1) "D"
 string(1) "3"
 string(1) "4"
+string(1) "0"
+string(1) "1"