diff --git a/.php_cs.dist.php b/.php_cs.dist.php
index 53a16da23..40a8ea8b9 100644
--- a/.php_cs.dist.php
+++ b/.php_cs.dist.php
@@ -31,7 +31,7 @@ $riskyRules = [
     //    'comment_to_phpdoc' => false,
     //    'no_unset_on_property' => false,
     'strict_param' => false,
-    'native_constant_invocation' => false,
+    //    'native_constant_invocation' => false,
     'php_unit_test_annotation' => false,
     'php_unit_no_expectation_annotation' => false,
     'declare_strict_types' => false,
@@ -46,8 +46,8 @@ $riskyRules = [
     //    'array_push' => false,
     'ereg_to_preg' => false,
     'error_suppression' => false,
-    'fopen_flag_order' => false,
-    'fopen_flags' => false,
+    //    'fopen_flag_order' => false,
+    //    'fopen_flags' => false,
     //    'logical_operators' => false,
     //    'modernize_types_casting' => false,
     //    'no_homoglyph_names' => false,
diff --git a/src/Bundle/ChillActivityBundle/Resources/test/Fixtures/App/web/app_dev.php b/src/Bundle/ChillActivityBundle/Resources/test/Fixtures/App/web/app_dev.php
index 5f3d50682..ba2ce9f21 100644
--- a/src/Bundle/ChillActivityBundle/Resources/test/Fixtures/App/web/app_dev.php
+++ b/src/Bundle/ChillActivityBundle/Resources/test/Fixtures/App/web/app_dev.php
@@ -18,7 +18,7 @@ use Symfony\Component\HttpFoundation\Request;
 // Feel free to remove this, extend it, or make something more sophisticated.
 if (isset($_SERVER['HTTP_CLIENT_IP'])
     || isset($_SERVER['HTTP_X_FORWARDED_FOR'])
-    || !(in_array(@$_SERVER['REMOTE_ADDR'], ['127.0.0.1', 'fe80::1', '::1']) || PHP_SAPI === 'cli-server')
+    || !(in_array(@$_SERVER['REMOTE_ADDR'], ['127.0.0.1', 'fe80::1', '::1']) || \PHP_SAPI === 'cli-server')
 ) {
     header('HTTP/1.0 403 Forbidden');
 
diff --git a/src/Bundle/ChillCustomFieldsBundle/Form/DataTransformer/JsonCustomFieldToArrayTransformer.php b/src/Bundle/ChillCustomFieldsBundle/Form/DataTransformer/JsonCustomFieldToArrayTransformer.php
index 86ac35cee..095c6f463 100644
--- a/src/Bundle/ChillCustomFieldsBundle/Form/DataTransformer/JsonCustomFieldToArrayTransformer.php
+++ b/src/Bundle/ChillCustomFieldsBundle/Form/DataTransformer/JsonCustomFieldToArrayTransformer.php
@@ -15,6 +15,7 @@ use Chill\CustomFieldsBundle\Entity\CustomField;
 use Doctrine\Persistence\ObjectManager;
 use Symfony\Component\Form\DataTransformerInterface;
 use function array_key_exists;
+use const JSON_THROW_ON_ERROR;
 
 class JsonCustomFieldToArrayTransformer implements DataTransformerInterface
 {
diff --git a/src/Bundle/ChillCustomFieldsBundle/Resources/test/Fixtures/App/web/app_dev.php b/src/Bundle/ChillCustomFieldsBundle/Resources/test/Fixtures/App/web/app_dev.php
index 5f3d50682..ba2ce9f21 100644
--- a/src/Bundle/ChillCustomFieldsBundle/Resources/test/Fixtures/App/web/app_dev.php
+++ b/src/Bundle/ChillCustomFieldsBundle/Resources/test/Fixtures/App/web/app_dev.php
@@ -18,7 +18,7 @@ use Symfony\Component\HttpFoundation\Request;
 // Feel free to remove this, extend it, or make something more sophisticated.
 if (isset($_SERVER['HTTP_CLIENT_IP'])
     || isset($_SERVER['HTTP_X_FORWARDED_FOR'])
-    || !(in_array(@$_SERVER['REMOTE_ADDR'], ['127.0.0.1', 'fe80::1', '::1']) || PHP_SAPI === 'cli-server')
+    || !(in_array(@$_SERVER['REMOTE_ADDR'], ['127.0.0.1', 'fe80::1', '::1']) || \PHP_SAPI === 'cli-server')
 ) {
     header('HTTP/1.0 403 Forbidden');
 
diff --git a/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorController.php b/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorController.php
index 9899e90ea..5baf6e225 100644
--- a/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorController.php
+++ b/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorController.php
@@ -47,7 +47,7 @@ class DocGeneratorController extends AbstractController
 
         unlink($tmpfname);
 
-        $fileContent = fopen($tmpfname2, 'r'); // the generated file content
+        $fileContent = fopen($tmpfname2, 'rb'); // the generated file content
         $response = new Response(fread($fileContent, filesize($tmpfname2)));
 
         $disposition = HeaderUtils::makeDisposition(
diff --git a/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorTemplateController.php b/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorTemplateController.php
index 844b7db67..a130bcf15 100644
--- a/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorTemplateController.php
+++ b/src/Bundle/ChillDocGeneratorBundle/Controller/DocGeneratorTemplateController.php
@@ -76,7 +76,7 @@ class DocGeneratorTemplateController extends AbstractController
 
         unlink($tmpfname);
 
-        $fileContent = fopen($tmpfname2, 'r'); // the generated file content
+        $fileContent = fopen($tmpfname2, 'rb'); // the generated file content
 
         $genDocName = 'doc_' . sprintf('%010d', mt_rand()) . '.docx';
 
diff --git a/src/Bundle/ChillMainBundle/CRUD/Routing/CRUDRoutesLoader.php b/src/Bundle/ChillMainBundle/CRUD/Routing/CRUDRoutesLoader.php
index 5b342b2fa..398b28685 100644
--- a/src/Bundle/ChillMainBundle/CRUD/Routing/CRUDRoutesLoader.php
+++ b/src/Bundle/ChillMainBundle/CRUD/Routing/CRUDRoutesLoader.php
@@ -21,6 +21,7 @@ use function array_keys;
 use function array_search;
 use function count;
 use function in_array;
+use const ARRAY_FILTER_USE_BOTH;
 
 class CRUDRoutesLoader extends Loader
 {
diff --git a/src/Bundle/ChillMainBundle/Command/LoadPostalCodesCommand.php b/src/Bundle/ChillMainBundle/Command/LoadPostalCodesCommand.php
index 4145e375e..5d7b39acc 100644
--- a/src/Bundle/ChillMainBundle/Command/LoadPostalCodesCommand.php
+++ b/src/Bundle/ChillMainBundle/Command/LoadPostalCodesCommand.php
@@ -196,7 +196,7 @@ class LoadPostalCodesCommand extends Command
                     . 'have the right to read it.');
         }
 
-        $resource = fopen($filename, 'r');
+        $resource = fopen($filename, 'rb');
 
         if (false == $resource) {
             throw new RuntimeException("The file '{$filename}' could not be opened.");
diff --git a/src/Bundle/ChillMainBundle/Export/Formatter/CSVFormatter.php b/src/Bundle/ChillMainBundle/Export/Formatter/CSVFormatter.php
index 0320a3fa4..914fa15c3 100644
--- a/src/Bundle/ChillMainBundle/Export/Formatter/CSVFormatter.php
+++ b/src/Bundle/ChillMainBundle/Export/Formatter/CSVFormatter.php
@@ -228,7 +228,7 @@ class CSVFormatter implements FormatterInterface
         $content = [];
 
         // create a file pointer connected to the output stream
-        $output = fopen('php://output', 'w');
+        $output = fopen('php://output', 'wb');
 
         //title
         fputcsv($output, [$this->translator->trans($this->export->getTitle())]);
diff --git a/src/Bundle/ChillMainBundle/Export/Formatter/CSVListFormatter.php b/src/Bundle/ChillMainBundle/Export/Formatter/CSVListFormatter.php
index d5ded2c31..bd6573056 100644
--- a/src/Bundle/ChillMainBundle/Export/Formatter/CSVListFormatter.php
+++ b/src/Bundle/ChillMainBundle/Export/Formatter/CSVListFormatter.php
@@ -115,7 +115,7 @@ class CSVListFormatter implements FormatterInterface
         $this->exportData = $exportData;
         $this->formatterData = $formatterData;
 
-        $output = fopen('php://output', 'w');
+        $output = fopen('php://output', 'wb');
 
         $this->prepareHeaders($output);
 
diff --git a/src/Bundle/ChillMainBundle/Export/Formatter/CSVPivotedListFormatter.php b/src/Bundle/ChillMainBundle/Export/Formatter/CSVPivotedListFormatter.php
index 7b1c10709..65ea70e55 100644
--- a/src/Bundle/ChillMainBundle/Export/Formatter/CSVPivotedListFormatter.php
+++ b/src/Bundle/ChillMainBundle/Export/Formatter/CSVPivotedListFormatter.php
@@ -110,7 +110,7 @@ class CSVPivotedListFormatter implements FormatterInterface
         $this->exportData = $exportData;
         $this->formatterData = $formatterData;
 
-        $output = fopen('php://output', 'w');
+        $output = fopen('php://output', 'wb');
 
         $i = 1;
         $lines = [];
diff --git a/src/Bundle/ChillMainBundle/Export/Formatter/SpreadSheetFormatter.php b/src/Bundle/ChillMainBundle/Export/Formatter/SpreadSheetFormatter.php
index 1a6bd494e..0fefdbb34 100644
--- a/src/Bundle/ChillMainBundle/Export/Formatter/SpreadSheetFormatter.php
+++ b/src/Bundle/ChillMainBundle/Export/Formatter/SpreadSheetFormatter.php
@@ -204,7 +204,7 @@ class SpreadSheetFormatter implements FormatterInterface
         $this->tempfile = tempnam(sys_get_temp_dir(), '');
         $this->generateContent();
 
-        $f = fopen($this->tempfile, 'r');
+        $f = fopen($this->tempfile, 'rb');
         $response->setContent(stream_get_contents($f));
         fclose($f);
 
diff --git a/src/Bundle/ChillMainBundle/Export/Formatter/SpreadsheetListFormatter.php b/src/Bundle/ChillMainBundle/Export/Formatter/SpreadsheetListFormatter.php
index f6fbff62f..7b4ffb3f6 100644
--- a/src/Bundle/ChillMainBundle/Export/Formatter/SpreadsheetListFormatter.php
+++ b/src/Bundle/ChillMainBundle/Export/Formatter/SpreadsheetListFormatter.php
@@ -199,7 +199,7 @@ class SpreadsheetListFormatter implements FormatterInterface
         $tempfile = tempnam(sys_get_temp_dir(), '');
         $writer->save($tempfile);
 
-        $f = fopen($tempfile, 'r');
+        $f = fopen($tempfile, 'rb');
         $response->setContent(stream_get_contents($f));
         fclose($f);
 
diff --git a/src/Bundle/ChillMainBundle/Form/Type/Select2CountryType.php b/src/Bundle/ChillMainBundle/Form/Type/Select2CountryType.php
index e0fa0374c..59f6ab060 100644
--- a/src/Bundle/ChillMainBundle/Form/Type/Select2CountryType.php
+++ b/src/Bundle/ChillMainBundle/Form/Type/Select2CountryType.php
@@ -17,6 +17,8 @@ use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Component\OptionsResolver\OptionsResolver;
+use const SORT_FLAG_CASE;
+use const SORT_STRING;
 
 /**
  * Extends choice to allow adding select2 library on widget.
diff --git a/src/Bundle/ChillMainBundle/Form/Type/Select2LanguageType.php b/src/Bundle/ChillMainBundle/Form/Type/Select2LanguageType.php
index a74454172..be8df20fe 100644
--- a/src/Bundle/ChillMainBundle/Form/Type/Select2LanguageType.php
+++ b/src/Bundle/ChillMainBundle/Form/Type/Select2LanguageType.php
@@ -17,6 +17,8 @@ use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Component\OptionsResolver\OptionsResolver;
+use const SORT_FLAG_CASE;
+use const SORT_STRING;
 
 /**
  * Extends choice to allow adding select2 library on widget for languages (multiple).
diff --git a/src/Bundle/ChillMainBundle/Security/Authorization/AbstractChillVoter.php b/src/Bundle/ChillMainBundle/Security/Authorization/AbstractChillVoter.php
index ad58b058a..ac1b65f1f 100644
--- a/src/Bundle/ChillMainBundle/Security/Authorization/AbstractChillVoter.php
+++ b/src/Bundle/ChillMainBundle/Security/Authorization/AbstractChillVoter.php
@@ -15,6 +15,7 @@ use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
 use Symfony\Component\Security\Core\Authorization\Voter\Voter;
 use function get_class;
 use function in_array;
+use const E_USER_DEPRECATED;
 
 /**
  * Voter for Chill software.
diff --git a/src/Bundle/ChillMainBundle/Util/DateRangeCovering.php b/src/Bundle/ChillMainBundle/Util/DateRangeCovering.php
index b874339b1..387a2ba3d 100644
--- a/src/Bundle/ChillMainBundle/Util/DateRangeCovering.php
+++ b/src/Bundle/ChillMainBundle/Util/DateRangeCovering.php
@@ -22,6 +22,7 @@ use function array_unique;
 use function array_values;
 use function count;
 use function ksort;
+use const PHP_INT_MAX;
 
 /**
  * Utilities to compare date periods.
diff --git a/src/Bundle/ChillPersonBundle/Command/ImportPeopleFromCSVCommand.php b/src/Bundle/ChillPersonBundle/Command/ImportPeopleFromCSVCommand.php
index f4ffef120..d8da05328 100644
--- a/src/Bundle/ChillPersonBundle/Command/ImportPeopleFromCSVCommand.php
+++ b/src/Bundle/ChillPersonBundle/Command/ImportPeopleFromCSVCommand.php
@@ -44,6 +44,8 @@ use function get_class;
 use function in_array;
 use function is_array;
 use function json_decode;
+use const JSON_PRETTY_PRINT;
+use const LC_TIME;
 
 final class ImportPeopleFromCSVCommand extends Command
 {
@@ -771,7 +773,7 @@ final class ImportPeopleFromCSVCommand extends Command
                     . 'have the right to read it.');
         }
 
-        $resource = fopen($filename, 'r');
+        $resource = fopen($filename, 'rb');
 
         if (false == $resource) {
             throw new RuntimeException("The file '{$filename}' could not be opened.");
diff --git a/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php b/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php
index 43391cc43..98b7d42f2 100644
--- a/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php
+++ b/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php
@@ -41,6 +41,7 @@ use Symfony\Component\Validator\GroupSequenceProviderInterface;
 use UnexpectedValueException;
 use function count;
 use function in_array;
+use const SORT_REGULAR;
 
 /**
  * AccompanyingPeriod Class.
diff --git a/src/Bundle/ChillPersonBundle/EventListener/PersonEventListener.php b/src/Bundle/ChillPersonBundle/EventListener/PersonEventListener.php
index 393ed2096..d3b4beb47 100644
--- a/src/Bundle/ChillPersonBundle/EventListener/PersonEventListener.php
+++ b/src/Bundle/ChillPersonBundle/EventListener/PersonEventListener.php
@@ -13,6 +13,7 @@ namespace Chill\PersonBundle\EventListener;
 
 use Chill\PersonBundle\Entity\Person;
 use Chill\PersonBundle\Entity\PersonAltName;
+use const MB_CASE_TITLE;
 
 class PersonEventListener
 {
diff --git a/src/Bundle/ChillPersonBundle/Form/Type/Select2MaritalStatusType.php b/src/Bundle/ChillPersonBundle/Form/Type/Select2MaritalStatusType.php
index dcd7b9075..1e09c9b94 100644
--- a/src/Bundle/ChillPersonBundle/Form/Type/Select2MaritalStatusType.php
+++ b/src/Bundle/ChillPersonBundle/Form/Type/Select2MaritalStatusType.php
@@ -17,6 +17,8 @@ use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\OptionsResolver\OptionsResolver;
+use const SORT_FLAG_CASE;
+use const SORT_STRING;
 
 /**
  * A type to select the marital status.
diff --git a/src/Bundle/ChillPersonBundle/Resources/test/Fixtures/App/web/app_dev.php b/src/Bundle/ChillPersonBundle/Resources/test/Fixtures/App/web/app_dev.php
index 5f3d50682..ba2ce9f21 100644
--- a/src/Bundle/ChillPersonBundle/Resources/test/Fixtures/App/web/app_dev.php
+++ b/src/Bundle/ChillPersonBundle/Resources/test/Fixtures/App/web/app_dev.php
@@ -18,7 +18,7 @@ use Symfony\Component\HttpFoundation\Request;
 // Feel free to remove this, extend it, or make something more sophisticated.
 if (isset($_SERVER['HTTP_CLIENT_IP'])
     || isset($_SERVER['HTTP_X_FORWARDED_FOR'])
-    || !(in_array(@$_SERVER['REMOTE_ADDR'], ['127.0.0.1', 'fe80::1', '::1']) || PHP_SAPI === 'cli-server')
+    || !(in_array(@$_SERVER['REMOTE_ADDR'], ['127.0.0.1', 'fe80::1', '::1']) || \PHP_SAPI === 'cli-server')
 ) {
     header('HTTP/1.0 403 Forbidden');