minor symfony#8946 [OptionsResolver] Documented validation of array types (EVODelavega, wouterj)

This PR was merged into the 3.4 branch.

Discussion
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[OptionsResolver] Documented validation of array types

This continues symfony#6048 . The feature was finally merged into symfony 3.4 (congratz @EVODelavega!), so let's document it!

Related Symfony PR: symfony/symfony#17032

Commits
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cb12592 Merged new example in older example, removing some text
318e199 Fix typo
bf5d9d3 Document typed arrays in optionsresolver

Author: javiereguiluz

components/options_resolver.rst

@@ -317,14 +317,27 @@ correctly. To validate the types of the options, call
         public function configureOptions(OptionsResolver $resolver)
         {
             // ...
+
+            // specify one allowed type
             $resolver->setAllowedTypes('host', 'string');
+
+            // specify multiple allowed types
             $resolver->setAllowedTypes('port', array('null', 'int'));
+
+            // check all items in an array recursively for a type
+            $resolver->setAllowedTypes('dates', 'DateTime[]');
+            $resolver->setAllowedtypes('ports', 'int[]');
         }
     }
 
-For each option, you can define either just one type or an array of acceptable
-types. You can pass any type for which an ``is_<type>()`` function is defined
-in PHP. Additionally, you may pass fully qualified class or interface names.
+You can pass any type for which an ``is_<type>()`` function is defined in PHP.
+You may also pass fully qualified class or interface names (which is checked
+using ``instanceof``). Additionally, you can validate all items in an array
+recursively by suffixing the type with ``[]``.
+
+.. versionadded:: 3.4
+    Validating types of array items recursively was introduced in Symfony 3.4.
+    Prior to Symfony 3.4, only scalar values could be validated.
 
 If you pass an invalid option now, an
 :class:`Symfony\\Component\\OptionsResolver\\Exception\\InvalidOptionsException`