diff --git a/src/Data/Cardinality.php b/src/Data/Cardinality.php
index 1e07fd6380e..d574d222b0c 100644
--- a/src/Data/Cardinality.php
+++ b/src/Data/Cardinality.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data;
 
 /**
diff --git a/src/Data/DataInstance.php b/src/Data/DataInstance.php
index 97558ab26c0..4eba0beda8a 100644
--- a/src/Data/DataInstance.php
+++ b/src/Data/DataInstance.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file defines the Instance interface.
  *
diff --git a/src/Data/Dictionary/Category.php b/src/Data/Dictionary/Category.php
index 65bafaabbf6..45e405fd157 100644
--- a/src/Data/Dictionary/Category.php
+++ b/src/Data/Dictionary/Category.php
@@ -1,5 +1,5 @@
-<?php
-declare(strict_types=1);
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Dictionary;
 
 /**
diff --git a/src/Data/Dictionary/DictionaryItem.php b/src/Data/Dictionary/DictionaryItem.php
index 44015061007..3f08dea7a6f 100644
--- a/src/Data/Dictionary/DictionaryItem.php
+++ b/src/Data/Dictionary/DictionaryItem.php
@@ -1,5 +1,5 @@
-<?php
-declare(strict_types=1);
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Dictionary;
 
 use \LORIS\Data\Scope;
diff --git a/src/Data/Filter.php b/src/Data/Filter.php
index cd7e1fe9c8f..ad5c5f8d65e 100644
--- a/src/Data/Filter.php
+++ b/src/Data/Filter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file contains a definition of the Filter interface.
  *
diff --git a/src/Data/Filters/AccessibleResourceFilter.php b/src/Data/Filters/AccessibleResourceFilter.php
index ddc99596846..25d5010c614 100644
--- a/src/Data/Filters/AccessibleResourceFilter.php
+++ b/src/Data/Filters/AccessibleResourceFilter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Filters;
 
 /**
diff --git a/src/Data/Filters/HasAnyPermissionOrUserSiteMatch.php b/src/Data/Filters/HasAnyPermissionOrUserSiteMatch.php
index 9fd51b90265..3bb73990b14 100644
--- a/src/Data/Filters/HasAnyPermissionOrUserSiteMatch.php
+++ b/src/Data/Filters/HasAnyPermissionOrUserSiteMatch.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file provides an implementation of the UserSiteMatchWithPermission filter.
  *
diff --git a/src/Data/Filters/PhantomsFilter.php b/src/Data/Filters/PhantomsFilter.php
index 065b750d5b6..0fa0ee88d8a 100644
--- a/src/Data/Filters/PhantomsFilter.php
+++ b/src/Data/Filters/PhantomsFilter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * PHP Version 7
  *
diff --git a/src/Data/Filters/ScansFilter.php b/src/Data/Filters/ScansFilter.php
index ca83be8d87a..5d7b6a7c008 100644
--- a/src/Data/Filters/ScansFilter.php
+++ b/src/Data/Filters/ScansFilter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * PHP Version 7
  *
diff --git a/src/Data/Filters/UserProjectMatch.php b/src/Data/Filters/UserProjectMatch.php
index 335abc50a8c..91571ec281b 100644
--- a/src/Data/Filters/UserProjectMatch.php
+++ b/src/Data/Filters/UserProjectMatch.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file provides an implementation of the UserProjectMatch filter.
  *
diff --git a/src/Data/Filters/UserSiteMatch.php b/src/Data/Filters/UserSiteMatch.php
index 06775bdd2ae..d09924ff08e 100644
--- a/src/Data/Filters/UserSiteMatch.php
+++ b/src/Data/Filters/UserSiteMatch.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file provides an implementation of the UserSiteMatch filter.
  *
diff --git a/src/Data/MapIterator.php b/src/Data/MapIterator.php
index a9c8fc18b7c..0fb379ed1d9 100644
--- a/src/Data/MapIterator.php
+++ b/src/Data/MapIterator.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file defines a MapIterator implementation.
  *
diff --git a/src/Data/Mapper.php b/src/Data/Mapper.php
index a9a5445beed..e3b647b4aba 100644
--- a/src/Data/Mapper.php
+++ b/src/Data/Mapper.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Thie file defines the \LORIS\Data\Mapper interface.
  *
diff --git a/src/Data/Models/DicomSeriesDTO.php b/src/Data/Models/DicomSeriesDTO.php
index abc41caee6f..a1e7d998159 100644
--- a/src/Data/Models/DicomSeriesDTO.php
+++ b/src/Data/Models/DicomSeriesDTO.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File implements the DicomSeriesDTO class
  *
diff --git a/src/Data/Models/DicomTarDTO.php b/src/Data/Models/DicomTarDTO.php
index fd2f320d0fa..80fa2548e31 100644
--- a/src/Data/Models/DicomTarDTO.php
+++ b/src/Data/Models/DicomTarDTO.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File implements the DicomTarDTO class
  *
diff --git a/src/Data/Models/ImageDTO.php b/src/Data/Models/ImageDTO.php
index 65fd77b2c32..5afbe79b5ab 100644
--- a/src/Data/Models/ImageDTO.php
+++ b/src/Data/Models/ImageDTO.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File that describe the ImageDTO class
  *
diff --git a/src/Data/Models/RecordingDTO.php b/src/Data/Models/RecordingDTO.php
index 575bb95423d..85caf90969b 100644
--- a/src/Data/Models/RecordingDTO.php
+++ b/src/Data/Models/RecordingDTO.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File that describe the RecordingDTO class.
  *
diff --git a/src/Data/Provisioner.php b/src/Data/Provisioner.php
index 8ef3e9c5616..cbf2f4e75d8 100644
--- a/src/Data/Provisioner.php
+++ b/src/Data/Provisioner.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file defines the concept of a data Provisioner.
  *
diff --git a/src/Data/ProvisionerInstance.php b/src/Data/ProvisionerInstance.php
index e0e4eb38ded..1e7d711b844 100644
--- a/src/Data/ProvisionerInstance.php
+++ b/src/Data/ProvisionerInstance.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file defines a helper for implementing the \LORIS\Data\Provisioner
  * interface.
diff --git a/src/Data/Provisioners/DBObjectProvisioner.php b/src/Data/Provisioners/DBObjectProvisioner.php
index bb75f9dc77f..823a0b4af0e 100644
--- a/src/Data/Provisioners/DBObjectProvisioner.php
+++ b/src/Data/Provisioners/DBObjectProvisioner.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * PHP Version 7
  *
diff --git a/src/Data/Provisioners/DBRowProvisioner.php b/src/Data/Provisioners/DBRowProvisioner.php
index 22c7bc9b0a4..5221c29cdf7 100644
--- a/src/Data/Provisioners/DBRowProvisioner.php
+++ b/src/Data/Provisioners/DBRowProvisioner.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * File defines a DBRowProvisioner, which is a type of provisioner that
  * gets data from an SQL database
diff --git a/src/Data/Provisioners/TimepointImagesRowProvisioner.php b/src/Data/Provisioners/TimepointImagesRowProvisioner.php
index 9c4a84b32cc..1562d6b50d7 100644
--- a/src/Data/Provisioners/TimepointImagesRowProvisioner.php
+++ b/src/Data/Provisioners/TimepointImagesRowProvisioner.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * This file implements a data provisioner to get all images
  * of a visit.
diff --git a/src/Data/Provisioners/TimepointRecordingsRowProvisioner.php b/src/Data/Provisioners/TimepointRecordingsRowProvisioner.php
index 9c7d53b2113..6b0943ce736 100644
--- a/src/Data/Provisioners/TimepointRecordingsRowProvisioner.php
+++ b/src/Data/Provisioners/TimepointRecordingsRowProvisioner.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * This file implements a data provisioner to get all images
  * of a visit.
diff --git a/src/Data/Query/Criteria.php b/src/Data/Query/Criteria.php
index b48080b6bd3..756632286cc 100644
--- a/src/Data/Query/Criteria.php
+++ b/src/Data/Query/Criteria.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Query;
 
 /**
diff --git a/src/Data/Query/Criteria/EndsWith.php b/src/Data/Query/Criteria/EndsWith.php
index 86380453ae3..89f0956e582 100644
--- a/src/Data/Query/Criteria/EndsWith.php
+++ b/src/Data/Query/Criteria/EndsWith.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/Equal.php b/src/Data/Query/Criteria/Equal.php
index e041db4e32f..3bb03e84a07 100644
--- a/src/Data/Query/Criteria/Equal.php
+++ b/src/Data/Query/Criteria/Equal.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Query\Criteria;
 
 use LORIS\Data\Query\Criteria;
diff --git a/src/Data/Query/Criteria/GreaterThan.php b/src/Data/Query/Criteria/GreaterThan.php
index d9c02b6fd65..b6ae15407b3 100644
--- a/src/Data/Query/Criteria/GreaterThan.php
+++ b/src/Data/Query/Criteria/GreaterThan.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Query\Criteria;
 
 use LORIS\Data\Query\Criteria;
diff --git a/src/Data/Query/Criteria/GreaterThanOrEqual.php b/src/Data/Query/Criteria/GreaterThanOrEqual.php
index a53ee2df13e..2a374243af5 100644
--- a/src/Data/Query/Criteria/GreaterThanOrEqual.php
+++ b/src/Data/Query/Criteria/GreaterThanOrEqual.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Query\Criteria;
 
 use LORIS\Data\Query\Criteria;
diff --git a/src/Data/Query/Criteria/In.php b/src/Data/Query/Criteria/In.php
index a1c8286e871..a80a963073e 100644
--- a/src/Data/Query/Criteria/In.php
+++ b/src/Data/Query/Criteria/In.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/IsNull.php b/src/Data/Query/Criteria/IsNull.php
index 27cf14c521d..f9c6b8ac010 100644
--- a/src/Data/Query/Criteria/IsNull.php
+++ b/src/Data/Query/Criteria/IsNull.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/LessThan.php b/src/Data/Query/Criteria/LessThan.php
index b3ae39f57a3..72c00778fb9 100644
--- a/src/Data/Query/Criteria/LessThan.php
+++ b/src/Data/Query/Criteria/LessThan.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/LessThanOrEqual.php b/src/Data/Query/Criteria/LessThanOrEqual.php
index 7d5686773db..4539e3bd526 100644
--- a/src/Data/Query/Criteria/LessThanOrEqual.php
+++ b/src/Data/Query/Criteria/LessThanOrEqual.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/NotEqual.php b/src/Data/Query/Criteria/NotEqual.php
index 3665b3e4571..12df3c97214 100644
--- a/src/Data/Query/Criteria/NotEqual.php
+++ b/src/Data/Query/Criteria/NotEqual.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/NotNull.php b/src/Data/Query/Criteria/NotNull.php
index 07582513ad7..1f58a953e6a 100644
--- a/src/Data/Query/Criteria/NotNull.php
+++ b/src/Data/Query/Criteria/NotNull.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/StartsWith.php b/src/Data/Query/Criteria/StartsWith.php
index 48f103799b1..48d0f2d0851 100644
--- a/src/Data/Query/Criteria/StartsWith.php
+++ b/src/Data/Query/Criteria/StartsWith.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/Criteria/Substring.php b/src/Data/Query/Criteria/Substring.php
index db63dc171da..50c94909297 100644
--- a/src/Data/Query/Criteria/Substring.php
+++ b/src/Data/Query/Criteria/Substring.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 namespace LORIS\Data\Query\Criteria;
 
diff --git a/src/Data/Query/NullQueryEngine.php b/src/Data/Query/NullQueryEngine.php
index 744b2f7802e..2f8bde8b24f 100644
--- a/src/Data/Query/NullQueryEngine.php
+++ b/src/Data/Query/NullQueryEngine.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Data\Query;
 
 use \LORIS\Data\Dictionary\DictionaryItem;
diff --git a/src/Data/Query/QueryEngine.php b/src/Data/Query/QueryEngine.php
index 62c9fd8a018..da4e235c873 100644
--- a/src/Data/Query/QueryEngine.php
+++ b/src/Data/Query/QueryEngine.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Data\Query;
 
 use \LORIS\StudyEntities\Candidate\CandID;
diff --git a/src/Data/Query/QueryTerm.php b/src/Data/Query/QueryTerm.php
index 8ad711f47ce..8b97d61143d 100644
--- a/src/Data/Query/QueryTerm.php
+++ b/src/Data/Query/QueryTerm.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Query;
 
 use LORIS\Data\Dictionary\DictionaryItem;
diff --git a/src/Data/Query/SQLQueryEngine.php b/src/Data/Query/SQLQueryEngine.php
index 8ba3fa81a9e..5db1e28e59f 100644
--- a/src/Data/Query/SQLQueryEngine.php
+++ b/src/Data/Query/SQLQueryEngine.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Data\Query;
 
 use LORIS\StudyEntities\Candidate\CandID;
diff --git a/src/Data/Scope.php b/src/Data/Scope.php
index c4327df27be..4adb5101854 100644
--- a/src/Data/Scope.php
+++ b/src/Data/Scope.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data;
 
 /**
diff --git a/src/Data/Table.php b/src/Data/Table.php
index c2f6521559b..66a43122642 100644
--- a/src/Data/Table.php
+++ b/src/Data/Table.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file implements the Table class.
  *
diff --git a/src/Data/Type.php b/src/Data/Type.php
index 65b5306b7db..38ed272354f 100644
--- a/src/Data/Type.php
+++ b/src/Data/Type.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data;
 
 /**
diff --git a/src/Data/Types/BooleanType.php b/src/Data/Types/BooleanType.php
index 46090756613..816b550e759 100644
--- a/src/Data/Types/BooleanType.php
+++ b/src/Data/Types/BooleanType.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/DateType.php b/src/Data/Types/DateType.php
index 037213ab847..1d9dd0599e0 100644
--- a/src/Data/Types/DateType.php
+++ b/src/Data/Types/DateType.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/DecimalType.php b/src/Data/Types/DecimalType.php
index d78a10498d5..abc25259556 100644
--- a/src/Data/Types/DecimalType.php
+++ b/src/Data/Types/DecimalType.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/Duration.php b/src/Data/Types/Duration.php
index 71c9718edcd..f048cab6bb0 100644
--- a/src/Data/Types/Duration.php
+++ b/src/Data/Types/Duration.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/Enumeration.php b/src/Data/Types/Enumeration.php
index c46561d9d51..0889c211b7c 100644
--- a/src/Data/Types/Enumeration.php
+++ b/src/Data/Types/Enumeration.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/IntegerType.php b/src/Data/Types/IntegerType.php
index a7aa20cbc87..2f861a5e54f 100644
--- a/src/Data/Types/IntegerType.php
+++ b/src/Data/Types/IntegerType.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/StringType.php b/src/Data/Types/StringType.php
index 0f2e2553036..cbedb1caf2c 100644
--- a/src/Data/Types/StringType.php
+++ b/src/Data/Types/StringType.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/TimeType.php b/src/Data/Types/TimeType.php
index ab4b0faa04c..245e6b1b9e4 100644
--- a/src/Data/Types/TimeType.php
+++ b/src/Data/Types/TimeType.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Data/Types/URI.php b/src/Data/Types/URI.php
index e0346f8a6cc..756d94b9677 100644
--- a/src/Data/Types/URI.php
+++ b/src/Data/Types/URI.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Data\Types;
 
 /**
diff --git a/src/Database/Query.php b/src/Database/Query.php
index cff0780cf87..64c8baabe28 100644
--- a/src/Database/Query.php
+++ b/src/Database/Query.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Database;
 
 class Query implements \Countable, \IteratorAggregate
diff --git a/src/GUI/MenuItem.php b/src/GUI/MenuItem.php
index 0c167c07cfb..4dadca37c41 100644
--- a/src/GUI/MenuItem.php
+++ b/src/GUI/MenuItem.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\GUI;
 
 /**
diff --git a/src/GUI/Widget.php b/src/GUI/Widget.php
index 401fff7f7b6..a2afb2c2943 100644
--- a/src/GUI/Widget.php
+++ b/src/GUI/Widget.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\GUI;
 
 /**
diff --git a/src/Http/Client.php b/src/Http/Client.php
index ab0343a14e3..e9947b52ddb 100644
--- a/src/Http/Client.php
+++ b/src/Http/Client.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
 * File contains the PSR18 HTTP Client implementation that
 * can be constructed with the "new" keyword.
diff --git a/src/Http/DataIteratorBinaryStream.php b/src/Http/DataIteratorBinaryStream.php
index 01e6fcbf385..92e056b9e20 100644
--- a/src/Http/DataIteratorBinaryStream.php
+++ b/src/Http/DataIteratorBinaryStream.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Http;
 
 use \Psr\Http\Message\StreamInterface;
diff --git a/src/Http/EmptyStream.php b/src/Http/EmptyStream.php
index 979eae4a9c3..6a78e5cba18 100644
--- a/src/Http/EmptyStream.php
+++ b/src/Http/EmptyStream.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * File contains the EmptyStream implementation.
  *
diff --git a/src/Http/Endpoint.php b/src/Http/Endpoint.php
index 9c33b180eaf..f1bd28f7825 100644
--- a/src/Http/Endpoint.php
+++ b/src/Http/Endpoint.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Http;
 
 use \Psr\Http\Message\ServerRequestInterface;
diff --git a/src/Http/Error.php b/src/Http/Error.php
index 18eb5e408ab..05b1daf3088 100644
--- a/src/Http/Error.php
+++ b/src/Http/Error.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file implements a HTTP error, a simple wrapper which provide
  * a html response using smarthy templates. It rely on the Diactoros implementation
diff --git a/src/Http/FileStream.php b/src/Http/FileStream.php
index 3ee7e38dde2..df5657d1dce 100644
--- a/src/Http/FileStream.php
+++ b/src/Http/FileStream.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file implements a FileStream, a simple wrapper which converts
  * a file into a PSR7 StreamInterface compatible with other PSR7
diff --git a/src/Http/FilesPassthroughEndpoint.php b/src/Http/FilesPassthroughEndpoint.php
index 3e1c6ace7cf..e5415072957 100644
--- a/src/Http/FilesPassthroughEndpoint.php
+++ b/src/Http/FilesPassthroughEndpoint.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Http;
 
 use \Psr\Http\Message\ServerRequestInterface;
diff --git a/src/Http/GzipStream.php b/src/Http/GzipStream.php
index 5aef9be8c4b..4339637c802 100644
--- a/src/Http/GzipStream.php
+++ b/src/Http/GzipStream.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Http;
 
 /**
diff --git a/src/Http/Request.php b/src/Http/Request.php
index 3546113030d..b4c7f79f355 100644
--- a/src/Http/Request.php
+++ b/src/Http/Request.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
 * File contains the PSR15 RequestInterface implementation that
 * can be constructed with the "new" keyword.
diff --git a/src/Http/Response.php b/src/Http/Response.php
index 48366895778..49f38289b4c 100644
--- a/src/Http/Response.php
+++ b/src/Http/Response.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
 * File contains the PSR15 ResponseInterface implementation that
 * can be constructed with the "new" keyword.
diff --git a/src/Http/Response/JSON/BadRequest.php b/src/Http/Response/JSON/BadRequest.php
index 88d71968839..853ce9175d5 100644
--- a/src/Http/Response/JSON/BadRequest.php
+++ b/src/Http/Response/JSON/BadRequest.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR7 ResponseInterface implementation for
  * Bad Request responses.
diff --git a/src/Http/Response/JSON/Conflict.php b/src/Http/Response/JSON/Conflict.php
index b4a3c682767..30d823a9ceb 100644
--- a/src/Http/Response/JSON/Conflict.php
+++ b/src/Http/Response/JSON/Conflict.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Conflict responses.
diff --git a/src/Http/Response/JSON/Created.php b/src/Http/Response/JSON/Created.php
index f0a1d560869..aedf9c97bca 100644
--- a/src/Http/Response/JSON/Created.php
+++ b/src/Http/Response/JSON/Created.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR7 ResponseInterface implementation for
  * Created responses.
diff --git a/src/Http/Response/JSON/Forbidden.php b/src/Http/Response/JSON/Forbidden.php
index 03db1b8d9ff..74862b9fd96 100644
--- a/src/Http/Response/JSON/Forbidden.php
+++ b/src/Http/Response/JSON/Forbidden.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
 * File contains the PSR15 ResponseInterface implementation for
 * Forbidden responses.
diff --git a/src/Http/Response/JSON/InternalServerError.php b/src/Http/Response/JSON/InternalServerError.php
index 5914c5bb54e..89ce5c970d6 100644
--- a/src/Http/Response/JSON/InternalServerError.php
+++ b/src/Http/Response/JSON/InternalServerError.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Internal Server Error responses.
diff --git a/src/Http/Response/JSON/MethodNotAllowed.php b/src/Http/Response/JSON/MethodNotAllowed.php
index 4b6d393d4d0..7579386494e 100644
--- a/src/Http/Response/JSON/MethodNotAllowed.php
+++ b/src/Http/Response/JSON/MethodNotAllowed.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Method Not Allowed responses.
diff --git a/src/Http/Response/JSON/NoContent.php b/src/Http/Response/JSON/NoContent.php
index 540d0c0c8b6..8a3ee58dc1e 100644
--- a/src/Http/Response/JSON/NoContent.php
+++ b/src/Http/Response/JSON/NoContent.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * No Content responses.
diff --git a/src/Http/Response/JSON/NotFound.php b/src/Http/Response/JSON/NotFound.php
index 700e81490ca..b2151563e37 100644
--- a/src/Http/Response/JSON/NotFound.php
+++ b/src/Http/Response/JSON/NotFound.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Not Found responses.
diff --git a/src/Http/Response/JSON/NotImplemented.php b/src/Http/Response/JSON/NotImplemented.php
index f984c78c19b..cbdb63b22c7 100644
--- a/src/Http/Response/JSON/NotImplemented.php
+++ b/src/Http/Response/JSON/NotImplemented.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Not Implemented responses.
diff --git a/src/Http/Response/JSON/NotModified.php b/src/Http/Response/JSON/NotModified.php
index 53b7eb49971..2689ade83e9 100644
--- a/src/Http/Response/JSON/NotModified.php
+++ b/src/Http/Response/JSON/NotModified.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Not Modified responses.
diff --git a/src/Http/Response/JSON/OK.php b/src/Http/Response/JSON/OK.php
index 14245bb2b77..50551fdde47 100644
--- a/src/Http/Response/JSON/OK.php
+++ b/src/Http/Response/JSON/OK.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR7 ResponseInterface implementation for
  * OK responses.
diff --git a/src/Http/Response/JSON/Unauthorized.php b/src/Http/Response/JSON/Unauthorized.php
index 2c531e5d1dc..bd1b56c3a13 100644
--- a/src/Http/Response/JSON/Unauthorized.php
+++ b/src/Http/Response/JSON/Unauthorized.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Unauthorized responses.
diff --git a/src/Http/Response/JSON/UnsupportedMediaType.php b/src/Http/Response/JSON/UnsupportedMediaType.php
index facc9b42e41..1b238d20b21 100644
--- a/src/Http/Response/JSON/UnsupportedMediaType.php
+++ b/src/Http/Response/JSON/UnsupportedMediaType.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Unsupported Media Type
diff --git a/src/Http/Response/JsonResponse.php b/src/Http/Response/JsonResponse.php
index 5752195eb6f..b5b08466135 100644
--- a/src/Http/Response/JsonResponse.php
+++ b/src/Http/Response/JsonResponse.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File contains the PSR15 ResponseInterface implementation for
  * Json response
diff --git a/src/Http/StringStream.php b/src/Http/StringStream.php
index 12d13fd2105..758519e6497 100644
--- a/src/Http/StringStream.php
+++ b/src/Http/StringStream.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * This file implements a StringStream, a simple wrapper which converts
  * a PHP string into a PSR7 StreamInterface compatible with other PSR7
diff --git a/src/Middleware/AnonymousPageDecorationMiddleware.php b/src/Middleware/AnonymousPageDecorationMiddleware.php
index cfc6f366cb0..d9d5ab07db3 100644
--- a/src/Middleware/AnonymousPageDecorationMiddleware.php
+++ b/src/Middleware/AnonymousPageDecorationMiddleware.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Middleware;
 
 use \Psr\Http\Message\ServerRequestInterface;
diff --git a/src/Middleware/AuthMiddleware.php b/src/Middleware/AuthMiddleware.php
index f5b7dfbfa9c..45439dfa856 100644
--- a/src/Middleware/AuthMiddleware.php
+++ b/src/Middleware/AuthMiddleware.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements the AuthMiddleware middleware class
  *
diff --git a/src/Middleware/Authenticator.php b/src/Middleware/Authenticator.php
index 13d7b90cebc..f37c936bbcc 100644
--- a/src/Middleware/Authenticator.php
+++ b/src/Middleware/Authenticator.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Defines Authenticator interface to authenticate access
  * to incoming requests.
diff --git a/src/Middleware/Compression.php b/src/Middleware/Compression.php
index c9ddd0679cd..2d4f556aa53 100644
--- a/src/Middleware/Compression.php
+++ b/src/Middleware/Compression.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Middleware;
 
 use \Psr\Http\Message\ServerRequestInterface;
diff --git a/src/Middleware/ContentLength.php b/src/Middleware/ContentLength.php
index 1162dc8dc66..17f6e612a39 100644
--- a/src/Middleware/ContentLength.php
+++ b/src/Middleware/ContentLength.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements the ContentLength middleware class
  *
diff --git a/src/Middleware/ETag.php b/src/Middleware/ETag.php
index 24f3c942c75..e3f2a89d35a 100644
--- a/src/Middleware/ETag.php
+++ b/src/Middleware/ETag.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements the ContentLength middleware class
  *
diff --git a/src/Middleware/ETagCalculator.php b/src/Middleware/ETagCalculator.php
index 2c9e9a3c2f3..6fc0401d8d4 100644
--- a/src/Middleware/ETagCalculator.php
+++ b/src/Middleware/ETagCalculator.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Defines the ETagCalculator interface.
  *
diff --git a/src/Middleware/ExceptionHandlingMiddleware.php b/src/Middleware/ExceptionHandlingMiddleware.php
index 5f14aa07fe6..2d0d8dfaa5f 100644
--- a/src/Middleware/ExceptionHandlingMiddleware.php
+++ b/src/Middleware/ExceptionHandlingMiddleware.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\Middleware;
 
 use \Psr\Http\Message\ServerRequestInterface;
diff --git a/src/Middleware/MiddlewareChainer.php b/src/Middleware/MiddlewareChainer.php
index 8dea2d7ea2f..9e9a5804e9a 100644
--- a/src/Middleware/MiddlewareChainer.php
+++ b/src/Middleware/MiddlewareChainer.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * File defines the MiddlewareChainer interface.
  *
diff --git a/src/Middleware/MiddlewareChainerMixin.php b/src/Middleware/MiddlewareChainerMixin.php
index 51914f13ce5..1fcdbac2c9c 100644
--- a/src/Middleware/MiddlewareChainerMixin.php
+++ b/src/Middleware/MiddlewareChainerMixin.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * Defines a MiddlewareChainerMixin trait to aid in the
  * implementation of Middleware chains.
diff --git a/src/Middleware/PageDecorationMiddleware.php b/src/Middleware/PageDecorationMiddleware.php
index 110a00175e3..ddcdcddc5cd 100644
--- a/src/Middleware/PageDecorationMiddleware.php
+++ b/src/Middleware/PageDecorationMiddleware.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Middleware;
 
 use \Psr\Http\Message\ServerRequestInterface;
diff --git a/src/Middleware/ResponseGenerator.php b/src/Middleware/ResponseGenerator.php
index a3859f5699c..4d959ed68fd 100644
--- a/src/Middleware/ResponseGenerator.php
+++ b/src/Middleware/ResponseGenerator.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements the ResponseGenerator middleware class
  *
diff --git a/src/Middleware/UserPageDecorationMiddleware.php b/src/Middleware/UserPageDecorationMiddleware.php
index 567e913b2ac..93d12b29f0c 100644
--- a/src/Middleware/UserPageDecorationMiddleware.php
+++ b/src/Middleware/UserPageDecorationMiddleware.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Middleware;
 
 use \Psr\Http\Message\ServerRequestInterface;
diff --git a/src/Router/BaseRouter.php b/src/Router/BaseRouter.php
index ca0bd628f4f..c136446e62d 100644
--- a/src/Router/BaseRouter.php
+++ b/src/Router/BaseRouter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements BaseRouter, a Router to handle the base of a LORIS
  * install.
diff --git a/src/Router/ModuleAuthenticator.php b/src/Router/ModuleAuthenticator.php
index ec83469fca3..a214400df31 100644
--- a/src/Router/ModuleAuthenticator.php
+++ b/src/Router/ModuleAuthenticator.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * File implements the ModuleAuthenticator class.
  *
diff --git a/src/Router/ModuleFileRouter.php b/src/Router/ModuleFileRouter.php
index 11443271381..e182abd9882 100644
--- a/src/Router/ModuleFileRouter.php
+++ b/src/Router/ModuleFileRouter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements ModuleFileRouter, a class for routing to files
  * directly stored on the file system.
diff --git a/src/Router/ModuleRouter.php b/src/Router/ModuleRouter.php
index 877f7fa11f2..4d57cbc3d70 100644
--- a/src/Router/ModuleRouter.php
+++ b/src/Router/ModuleRouter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements ModuleRouter, a class for routing to a specific
  * module.
diff --git a/src/Router/NoopResponder.php b/src/Router/NoopResponder.php
index e335c9061c0..f69d8c8e107 100644
--- a/src/Router/NoopResponder.php
+++ b/src/Router/NoopResponder.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 namespace LORIS\Router;
 
 use \Psr\Http\Server\RequestHandlerInterface;
diff --git a/src/Router/PrefixRouter.php b/src/Router/PrefixRouter.php
index c40088dfd59..f9983669a6f 100644
--- a/src/Router/PrefixRouter.php
+++ b/src/Router/PrefixRouter.php
@@ -1,4 +1,5 @@
-<?php
+<?php declare(strict_types=1);
+
 /**
  * Implements PrefixRouter, a class for handling prefixes
  * of a URL and then delegating to other request handlers.
diff --git a/src/StudyEntities/AccessibleResource.php b/src/StudyEntities/AccessibleResource.php
index 4aa7eb1c54c..8ae91f5546c 100644
--- a/src/StudyEntities/AccessibleResource.php
+++ b/src/StudyEntities/AccessibleResource.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\StudyEntities;
 
 /**
diff --git a/src/StudyEntities/Candidate/CandID.php b/src/StudyEntities/Candidate/CandID.php
index 48164f5f7f6..62b4af1dd9c 100644
--- a/src/StudyEntities/Candidate/CandID.php
+++ b/src/StudyEntities/Candidate/CandID.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * This defines what a CandID should be so it can be passed as a typed
  * parameter in functions.
diff --git a/src/StudyEntities/Candidate/EntityType.php b/src/StudyEntities/Candidate/EntityType.php
index c1e38bbf829..563e52c5d79 100644
--- a/src/StudyEntities/Candidate/EntityType.php
+++ b/src/StudyEntities/Candidate/EntityType.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * This defines the entity type property for a Candidate. It is a Value Object used
  * to assist with validation.
diff --git a/src/StudyEntities/Candidate/Identifier.php b/src/StudyEntities/Candidate/Identifier.php
index a496fc1de8b..9d03732f2a5 100644
--- a/src/StudyEntities/Candidate/Identifier.php
+++ b/src/StudyEntities/Candidate/Identifier.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * PHP Version 7
  *
diff --git a/src/StudyEntities/Candidate/Sex.php b/src/StudyEntities/Candidate/Sex.php
index 07e8f413fbf..a3d92a72545 100644
--- a/src/StudyEntities/Candidate/Sex.php
+++ b/src/StudyEntities/Candidate/Sex.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * This defines valid values for the Sex data point for a Candidate.
  * It is a Value Object used to assist with validation.
diff --git a/src/StudyEntities/Candidate/ValidatableIdentifier.php b/src/StudyEntities/Candidate/ValidatableIdentifier.php
index 7919ad0de1c..6dd7b9fd58e 100644
--- a/src/StudyEntities/Candidate/ValidatableIdentifier.php
+++ b/src/StudyEntities/Candidate/ValidatableIdentifier.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 /**
  * Implementation of ValidatableIdentifier needs to provide a validation
  * function to ensure that no Identifier of that type exists if the value is
diff --git a/src/StudyEntities/MultiSiteHaver.php b/src/StudyEntities/MultiSiteHaver.php
index 783f844fa61..0ab7eddc51b 100644
--- a/src/StudyEntities/MultiSiteHaver.php
+++ b/src/StudyEntities/MultiSiteHaver.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\StudyEntities;
 
 /**
diff --git a/src/StudyEntities/SiteHaver.php b/src/StudyEntities/SiteHaver.php
index f8aaa1c0225..7664c9577d5 100644
--- a/src/StudyEntities/SiteHaver.php
+++ b/src/StudyEntities/SiteHaver.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace LORIS\StudyEntities;
 
 /**
diff --git a/test/SrcCS.xml b/test/SrcCS.xml
index fd9cc0dc6ae..5b4cdb85aea 100644
--- a/test/SrcCS.xml
+++ b/test/SrcCS.xml
@@ -2,6 +2,16 @@
 <ruleset name="Loris Standard">
     <description>The coding standard for the Loris project</description>
 
+    <config name="installed_paths" value="../../slevomat/coding-standard"/>
+
+
+     <!-- Require strict types to be declared -->
+     <rule ref="SlevomatCodingStandard.TypeHints.DeclareStrictTypes">
+         <properties>
+             <property name="spacesCountAroundEqualsSign" value="0"/>
+         </properties>
+     </rule>
+
     <!-- Include the PSR2 standard -->
     <rule ref="PSR2"/>