From 7f28d7266f81985096219a11b949561d70f052e4 Mon Sep 17 00:00:00 2001
From: Andre Klapper <a9016009@gmx.de>
Date: Fri, 10 May 2024 12:04:39 +0200
Subject: [PATCH] Fix PHP 8.1 "preg_match(null)" exception for missing
 Content-Type

Summary:
When the `Content-Type` HTTP header is empty or missing, `null` is passed to `preg_match()` which is deprecated behavior since PHP 8.1. Thus only call `preg_match()` when the value is set.

```
ERROR 8192: preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated at [$HOME/arcanist/src/future/http/status/HTTPFutureHTTPResponseStatus.php:24]
```

Closes T15821

Test Plan: Visit something using `HTTPFutureHTTPResponseStatus`, like, a profile image. No crashes.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15821

Differential Revision: https://we.phorge.it/D25632
---
 src/future/http/status/HTTPFutureHTTPResponseStatus.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/future/http/status/HTTPFutureHTTPResponseStatus.php b/src/future/http/status/HTTPFutureHTTPResponseStatus.php
index 469f9a0c..44636dca 100644
--- a/src/future/http/status/HTTPFutureHTTPResponseStatus.php
+++ b/src/future/http/status/HTTPFutureHTTPResponseStatus.php
@@ -21,7 +21,8 @@ final class HTTPFutureHTTPResponseStatus extends HTTPFutureResponseStatus {
 
     $content_type = BaseHTTPFuture::getHeader($headers, 'Content-Type');
     $match = null;
-    if (preg_match('/;\s*charset=([^;]+)/', $content_type, $match)) {
+    if (phutil_nonempty_string($content_type) &&
+      preg_match('/;\s*charset=([^;]+)/', $content_type, $match)) {
       $encoding = trim($match[1], "\"'");
       try {
         $excerpt = phutil_utf8_convert($excerpt, 'UTF-8', $encoding);