Fix GH-18823: setlocale's 2nd and 3rd argument ignores strict_types

Author: ndossche

ext/standard/string.c

@@ -4933,6 +4933,15 @@ PHP_FUNCTION(setlocale)
 		Z_PARAM_VARIADIC('+', args, num_args)
 	ZEND_PARSE_PARAMETERS_END();
 
+	if (ZEND_ARG_USES_STRICT_TYPES()) {
+		for (uint32_t i = 0; i < num_args; i++) {
+			if (UNEXPECTED(Z_TYPE(args[i]) != IS_ARRAY && Z_TYPE(args[i]) != IS_STRING)) {
+				zend_wrong_parameter_type_error(i + 2, Z_EXPECTED_ARRAY_OR_STRING, &args[i]);
+				RETURN_THROWS();
+			}
+		}
+	}
+
 	for (uint32_t i = 0; i < num_args; i++) {
 		if (Z_TYPE(args[i]) == IS_ARRAY) {
 			zval *elem;

ext/standard/tests/strings/gh18823.phpt

@@ -0,0 +1,19 @@
+--TEST--
+GH-18823 (setlocale's 2nd and 3rd argument ignores strict_types)
+--FILE--
+<?php
+declare(strict_types=1);
+try {
+    setlocale(LC_ALL, 0, "0");
+} catch (TypeError $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    setlocale(LC_ALL, "0", 0);
+} catch (TypeError $e) {
+    echo $e->getMessage(), "\n";
+}
+?>
+--EXPECT--
+setlocale(): Argument #2 ($locales) must be of type array|string, int given
+setlocale(): Argument #3 must be of type array|string, int given