PHP 8.0 support

Author: grzesiekgorczyca

composer.json

@@ -10,7 +10,7 @@
         }
     },
     "require": {
-        "php": "^7.0",
+        "php": "^7.2 || ^8.0",
         "ext-json":  "*",
         "guzzlehttp/guzzle": "~7.2",
         "monolog/monolog": "^1.24|^2.0",
@@ -19,6 +19,6 @@
         "myclabs/php-enum": "^1.7"
     },
     "require-dev": {
-        "symfony/var-dumper": "^4.3"
+        "symfony/var-dumper": "^5.4"
     }
 }

composer.lock

@@ -25,7 +25,7 @@ public function __construct(string $name, string $value)
         }
 
         if (str_replace(" \n\r", '', $name) != $name) {
-            throw new InvalidHeaderException(sprintf('Invalid header name "%s", header contains whitespaces'));
+            throw new InvalidHeaderException(sprintf('Invalid header name "%s", header contains whitespaces', $name));
         }
 
         if (strtolower(substr($name, 0,2)) != 'x-') {

src/Messaging/Mail/Header.php

@@ -241,9 +241,9 @@ private function replaceContent(ContentType $contentType, string $body): void
 
     /**
      * @param ContentType $contentType
-     * @return string
+     * @return Content|null
      */
-    private function getContent(ContentType $contentType): Content
+    private function getContent(ContentType $contentType): ?Content
     {
         foreach ($this->contents as $content) {
             if ($content->getContentType() == $contentType) {