Fix GH-8924 str_split of empty string must return empty array

Closes #8945.

Author: mvorisek

NEWS

@@ -13,6 +13,9 @@ PHP                                                                        NEWS
 - FPM:
   . Added listen.setfib pool option to set route FIB on FreeBSD. (David Carlier)
 
+- Standard:
+  . Fixed empty array returned by str_split on empty input. (Michael Vorisek)
+
 07 Jul 2022, PHP 8.2.0alpha3
 
 - Core:

UPGRADING

@@ -45,6 +45,7 @@ PHP 8.2 UPGRADE NOTES
     stripos, strripos, lcfirst, ucfirst, ucwords, str_ireplace,
     array_change_key_case and sorting with SORT_FLAG_CASE use ASCII case
     conversion.
+  . str_split no longer returns an empty array on empty string.
 
 - SPL:
   . The following methods now enforce their signature:

ext/standard/string.c

@@ -5885,7 +5885,11 @@ PHP_FUNCTION(str_split)
 		RETURN_THROWS();
 	}
 
-	if (0 == ZSTR_LEN(str) || (size_t)split_length >= ZSTR_LEN(str)) {
+	if ((size_t)split_length >= ZSTR_LEN(str)) {
+		if (0 == ZSTR_LEN(str)) {
+			RETURN_EMPTY_ARRAY();
+		}
+
 		array_init_size(return_value, 1);
 		add_next_index_stringl(return_value, ZSTR_VAL(str), ZSTR_LEN(str));
 		return;

ext/standard/tests/strings/str_split_basic.phpt

@@ -16,7 +16,11 @@ var_dump( str_split($str,$split_length) );
 echo "-- With split_length as default argument --\n";
 var_dump( str_split($str) );
 
-echo "Done"
+echo "-- Empty string must always return empty array --\n";
+var_dump( str_split('') );
+var_dump( str_split('', 1) );
+var_dump( str_split('', 100) );
+
 ?>
 --EXPECT--
 *** Testing str_split() : basic functionality ***
@@ -80,4 +84,10 @@ array(22) {
   [21]=>
   string(1) "e"
 }
-Done
+-- Empty string must always return empty array --
+array(0) {
+}
+array(0) {
+}
+array(0) {
+}

ext/standard/tests/strings/str_split_variation3.phpt

@@ -39,9 +39,7 @@ echo "Done"
 --EXPECTF--
 *** Testing str_split() : double quoted strings for 'str' ***
 -- Iteration 1 --
-array(1) {
-  [0]=>
-  string(0) ""
+array(0) {
 }
 -- Iteration 2 --
 array(1) {

ext/standard/tests/strings/str_split_variation4.phpt

@@ -38,9 +38,7 @@ echo "Done"
 --EXPECT--
 *** Testing str_split() : single quoted strings for 'str' ***
 -- Iteration 1 --
-array(1) {
-  [0]=>
-  string(0) ""
+array(0) {
 }
 -- Iteration 2 --
 array(1) {

ext/standard/tests/strings/str_split_variation5.phpt

@@ -81,14 +81,10 @@ echo "Done"
 --EXPECT--
 *** Testing str_split() : heredoc strings as 'str' argument ***
 -- Iteration 1 --
-array(1) {
-  [0]=>
-  string(0) ""
+array(0) {
 }
 -- Iteration 2 --
-array(1) {
-  [0]=>
-  string(0) ""
+array(0) {
 }
 -- Iteration 3 --
 array(1) {