minor symfony#54189 [ErrorHandler] Fix exit code when an exception occurs and the exception handler has been unregistered (nicolas-grekas)

This PR was merged into the 5.4 branch.

Discussion
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[ErrorHandler] Fix exit code when an exception occurs and the exception handler has been unregistered

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix symfony#53946
| License       | MIT

PHP 8.3 introduced a change (see php/php-src#13446) that highlighted a fragility in ErrorHandler::handleFatalError, leading to the linked issued. This fixes it.

What this doesn't fix is turning fatal errors into fake exceptions, which PHP 8.3 broke. For this, the fix is on the side of PHP.

Testing is not obvious 🙈

Commits
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f4ea95d [ErrorHandler] Fix exit code when an exception occurs and the exception handler has been unregistered

Author: nicolas-grekas

src/Symfony/Component/ErrorHandler/ErrorHandler.php

@@ -669,6 +669,10 @@ public static function handleFatalError(?array $error = null): void
             set_exception_handler($h);
         }
         if (!$handler) {
+            if (null === $error && $exitCode = self::$exitCode) {
+                register_shutdown_function('register_shutdown_function', function () use ($exitCode) { exit($exitCode); });
+            }
+
             return;
         }
         if ($handler !== $h) {
@@ -704,8 +708,7 @@ public static function handleFatalError(?array $error = null): void
             // Ignore this re-throw
         }
 
-        if ($exit && self::$exitCode) {
-            $exitCode = self::$exitCode;
+        if ($exit && $exitCode = self::$exitCode) {
             register_shutdown_function('register_shutdown_function', function () use ($exitCode) { exit($exitCode); });
         }
     }