Support PHP 8.1

Author: SimonFrings

.github/workflows/ci.yml

@@ -11,6 +11,7 @@ jobs:
     strategy:
       matrix:
         php:
+          - 8.1
           - 8.0
           - 7.4
           - 7.3

phpunit.xml.dist

@@ -4,8 +4,9 @@
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
          xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
          bootstrap="vendor/autoload.php"
+         cacheResult="false"
          colors="true"
-         cacheResult="false">
+         convertDeprecationsToExceptions="true">
     <testsuites>
         <testsuite name="Http Proxy Test Suite">
             <directory>./tests/</directory>