[Doc] Use Markdown syntax highlighting

Author: lologhi

README.md

@@ -12,88 +12,96 @@ The following example demonstrates a Person class with two required options
 the default value of "gender" is derived from the passed first name, if
 possible, and may only be one of "male" and "female".
 
-    use Symfony\Component\OptionsResolver\OptionsResolver;
-    use Symfony\Component\OptionsResolver\OptionsResolverInterface;
-    use Symfony\Component\OptionsResolver\Options;
+```php
+use Symfony\Component\OptionsResolver\OptionsResolver;
+use Symfony\Component\OptionsResolver\OptionsResolverInterface;
+use Symfony\Component\OptionsResolver\Options;
 
-    class Person
+class Person
+{
+    protected $options;
+
+    public function __construct(array $options = array())
     {
-        protected $options;
-
-        public function __construct(array $options = array())
-        {
-            $resolver = new OptionsResolver();
-            $this->setDefaultOptions($resolver);
-
-            $this->options = $resolver->resolve($options);
-        }
-
-        protected function setDefaultOptions(OptionsResolverInterface $resolver)
-        {
-            $resolver->setRequired(array(
-                'firstName',
-                'lastName',
-            ));
-
-            $resolver->setDefaults(array(
-                'age' => null,
-                'gender' => function (Options $options) {
-                    if (self::isKnownMaleName($options['firstName'])) {
-                        return 'male';
-                    }
-
-                    return 'female';
-                },
-            ));
-
-            $resolver->setAllowedValues(array(
-                'gender' => array('male', 'female'),
-            ));
-        }
+        $resolver = new OptionsResolver();
+        $this->setDefaultOptions($resolver);
+
+        $this->options = $resolver->resolve($options);
     }
 
+    protected function setDefaultOptions(OptionsResolverInterface $resolver)
+    {
+        $resolver->setRequired(array(
+            'firstName',
+            'lastName',
+        ));
+
+        $resolver->setDefaults(array(
+            'age' => null,
+            'gender' => function (Options $options) {
+                if (self::isKnownMaleName($options['firstName'])) {
+                    return 'male';
+                }
+
+                return 'female';
+            },
+        ));
+
+        $resolver->setAllowedValues(array(
+            'gender' => array('male', 'female'),
+        ));
+    }
+}
+```
+
 We can now easily instantiate a Person object:
 
-    // 'gender' is implicitly set to 'female'
-    $person = new Person(array(
-        'firstName' => 'Jane',
-        'lastName' => 'Doe',
-    ));
+```php
+// 'gender' is implicitly set to 'female'
+$person = new Person(array(
+    'firstName' => 'Jane',
+    'lastName' => 'Doe',
+));
+```
 
 We can also override the default values of the optional options:
 
-    $person = new Person(array(
-        'firstName' => 'Abdullah',
-        'lastName' => 'Mogashi',
-        'gender' => 'male',
-        'age' => 30,
-    ));
+```php
+$person = new Person(array(
+    'firstName' => 'Abdullah',
+    'lastName' => 'Mogashi',
+    'gender' => 'male',
+    'age' => 30,
+));
+```
 
 Options can be added or changed in subclasses by overriding the `setDefaultOptions`
 method:
 
-    use Symfony\Component\OptionsResolver\OptionsResolver;
-    use Symfony\Component\OptionsResolver\Options;
+```php
+use Symfony\Component\OptionsResolver\OptionsResolver;
+use Symfony\Component\OptionsResolver\Options;
 
-    class Employee extends Person
+class Employee extends Person
+{
+    protected function setDefaultOptions(OptionsResolverInterface $resolver)
     {
-        protected function setDefaultOptions(OptionsResolverInterface $resolver)
-        {
-            parent::setDefaultOptions($resolver);
-
-            $resolver->setRequired(array(
-                'birthDate',
-            ));
-
-            $resolver->setDefaults(array(
-                // $previousValue contains the default value configured in the
-                // parent class
-                'age' => function (Options $options, $previousValue) {
-                    return self::calculateAge($options['birthDate']);
-                }
-            ));
-        }
+        parent::setDefaultOptions($resolver);
+
+        $resolver->setRequired(array(
+            'birthDate',
+        ));
+
+        $resolver->setDefaults(array(
+            // $previousValue contains the default value configured in the
+            // parent class
+            'age' => function (Options $options, $previousValue) {
+                return self::calculateAge($options['birthDate']);
+            }
+        ));
     }
+}
+```