Properly update string type flags

Author: dstogov

Zend/zend_variables.c

@@ -219,8 +219,10 @@ ZEND_API void ZEND_FASTCALL _zval_copy_ctor_func(zval *zvalue ZEND_FILE_LINE_DC)
 {
 	if (EXPECTED(Z_TYPE_P(zvalue) == IS_ARRAY)) {
 		ZVAL_ARR(zvalue, zend_array_dup(Z_ARRVAL_P(zvalue)));
-	} else if (EXPECTED(Z_TYPE_P(zvalue) == IS_STRING) ||
-	           EXPECTED(Z_TYPE_P(zvalue) == IS_CONSTANT)) {
+	} else if (EXPECTED(Z_TYPE_P(zvalue) == IS_STRING)) {
+		CHECK_ZVAL_STRING_REL(Z_STR_P(zvalue));
+		ZVAL_NEW_STR(zvalue, zend_string_dup(Z_STR_P(zvalue), 0));
+	} else if (EXPECTED(Z_TYPE_P(zvalue) == IS_CONSTANT)) {
 		CHECK_ZVAL_STRING_REL(Z_STR_P(zvalue));
 		Z_STR_P(zvalue) = zend_string_dup(Z_STR_P(zvalue), 0);
 	} else if (EXPECTED(Z_TYPE_P(zvalue) == IS_CONSTANT_AST)) {