minor #11012 [OptionsResolver] Updated some example code to use modern PHP (javiereguiluz)

This PR was squashed before being merged into the 4.2 branch (closes #11012).

Discussion
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[OptionsResolver] Updated some example code to use modern PHP

OptionsResolver is nice ... so we don't have to use unnecessarily bad PHP code to explain how nice it is.

Commits
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c555805 [OptionsResolver] Updated some example code to use modern PHP

Author: javiereguiluz

components/options_resolver.rst

@@ -36,7 +36,7 @@ Imagine you have a ``Mailer`` class which has four options: ``host``,
         }
     }
 
-When accessing the ``$options``, you need to add a lot of boilerplate code to
+When accessing the ``$options``, you need to add some boilerplate code to
 check which options are set::
 
     class Mailer
@@ -46,29 +46,17 @@ check which options are set::
         {
             $mail = ...;
 
-            $mail->setHost(isset($this->options['host'])
-                ? $this->options['host']
-                : 'smtp.example.org');
-
-            $mail->setUsername(isset($this->options['username'])
-                ? $this->options['username']
-                : 'user');
-
-            $mail->setPassword(isset($this->options['password'])
-                ? $this->options['password']
-                : 'pa$$word');
-
-            $mail->setPort(isset($this->options['port'])
-                ? $this->options['port']
-                : 25);
+            $mail->setHost($this->options['host'] ?? 'smtp.example.org');
+            $mail->setUsername($this->options['username'] ?? 'user');
+            $mail->setPassword($this->options['password'] ?? 'pa$$word');
+            $mail->setPort($this->options['port'] ?? 25);
 
             // ...
         }
     }
 
-This boilerplate is hard to read and repetitive. Also, the default values of the
-options are buried in the business logic of your code. Use the
-:phpfunction:`array_replace` to fix that::
+Also, the default values of the options are buried in the business logic of your
+code. Use the :phpfunction:`array_replace` to fix that::
 
     class Mailer
     {