[2.7] [Form] Replaced calls to array_search() by in_array() where is no need to get the index

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

src/Symfony/Bridge/Twig/Extension/FormExtension.php

@@ -144,7 +144,7 @@ class FormExtension extends \Twig_Extension
     public function isSelectedChoice(ChoiceView $choice, $selectedValue)
     {
         if (is_array($selectedValue)) {
-            return false !== array_search($choice->value, $selectedValue, true);
+            return in_array($choice->value, $selectedValue, true);
         }
 
         return $choice->value === $selectedValue;

src/Symfony/Component/Form/Extension/Core/ChoiceList/ChoiceList.php

@@ -381,7 +381,7 @@ class ChoiceList implements ChoiceListInterface
      */
     protected function isPreferred($choice, array $preferredChoices)
     {
-        return false !== array_search($choice, $preferredChoices, true);
+        return in_array($choice, $preferredChoices, true);
     }
 
     /**

src/Symfony/Component/Form/Extension/Core/Type/ChoiceType.php

@@ -111,7 +111,7 @@ class ChoiceType extends AbstractType
         // avoid making the type check inside the closure.
         if ($options['multiple']) {
             $view->vars['is_selected'] = function ($choice, array $values) {
-                return false !== array_search($choice, $values, true);
+                return in_array($choice, $values, true);
             };
         } else {
             $view->vars['is_selected'] = function ($choice, $value) {