diff --git a/application/Espo/Core/Formula/ArgumentList.php b/application/Espo/Core/Formula/ArgumentList.php
index 82633db1da..5e0ee9c143 100644
--- a/application/Espo/Core/Formula/ArgumentList.php
+++ b/application/Espo/Core/Formula/ArgumentList.php
@@ -67,7 +67,7 @@ class ArgumentList implements Evaluatable, Iterator, Countable, ArrayAccess, See
         return $i;
     }
 
-    public function rewind()
+    public function rewind(): void
     {
         $this->position = 0;
 
@@ -81,22 +81,32 @@ class ArgumentList implements Evaluatable, Iterator, Countable, ArrayAccess, See
         return new Argument($this->dataList[$index]);
     }
 
+    /**
+     * @return mixed
+     */
     public function current()
     {
         return $this->getArgumentByIndex($this->position);
     }
 
+    /**
+     * @return mixed
+     */
     public function key()
     {
         return $this->position;
     }
 
-    public function next()
+    public function next(): void
     {
         do {
             $this->position ++;
             $next = false;
-            if (!$this->valid() && $this->position <= $this->getLastValidKey()) {
+
+            if (
+                !$this->valid() &&
+                $this->position <= $this->getLastValidKey()
+            ) {
                 $next = true;
             }
         } while ($next);
@@ -107,11 +117,18 @@ class ArgumentList implements Evaluatable, Iterator, Countable, ArrayAccess, See
         return array_key_exists($this->position, $this->dataList);
     }
 
+    /**
+     * @param mixed $offset
+     */
     public function offsetExists($offset): bool
     {
         return array_key_exists($offset, $this->dataList);
     }
 
+    /**
+     * @param mixed $offset
+     * @return mixed
+     */
     public function offsetGet($offset)
     {
         if (!$this->offsetExists($offset)) {
@@ -120,12 +137,19 @@ class ArgumentList implements Evaluatable, Iterator, Countable, ArrayAccess, See
         return $this->getArgumentByIndex($offset);
     }
 
-    public function offsetSet($offset, $value)
+    /**
+     * @param mixed $offset
+     * @param mixed $value
+     */
+    public function offsetSet($offset, $value): void
     {
         throw new BadMethodCallException('Setting is not allowed.');
     }
 
-    public function offsetUnset($offset)
+    /**
+     * @param mixed $offset
+     */
+    public function offsetUnset($offset): void
     {
         throw new BadMethodCallException('Unsetting is not allowed.');
     }
@@ -135,7 +159,10 @@ class ArgumentList implements Evaluatable, Iterator, Countable, ArrayAccess, See
         return count($this->dataList);
     }
 
-    public function seek($offset)
+    /**
+     * @param int $offset
+     */
+    public function seek($offset): void
     {
         $this->position = $offset;
 
diff --git a/application/Espo/ORM/EntityCollection.php b/application/Espo/ORM/EntityCollection.php
index d07277e1e0..103337f954 100644
--- a/application/Espo/ORM/EntityCollection.php
+++ b/application/Espo/ORM/EntityCollection.php
@@ -65,7 +65,7 @@ class EntityCollection implements Collection, Iterator, Countable, ArrayAccess,
         $this->entityFactory = $entityFactory;
     }
 
-    public function rewind()
+    public function rewind(): void
     {
         $this->position = 0;
 
@@ -74,17 +74,23 @@ class EntityCollection implements Collection, Iterator, Countable, ArrayAccess,
         }
     }
 
+    /**
+     * @return mixed
+     */
     public function current()
     {
         return $this->getEntityByOffset($this->position);
     }
 
+    /**
+     * @return mixed
+     */
     public function key()
     {
         return $this->position;
     }
 
-    public function next()
+    public function next(): void
     {
         do {
             $this->position ++;
@@ -114,16 +120,23 @@ class EntityCollection implements Collection, Iterator, Countable, ArrayAccess,
         return $i;
     }
 
-    public function valid()
+    public function valid(): bool
     {
         return isset($this->dataList[$this->position]);
     }
 
-    public function offsetExists($offset)
+    /**
+     * @param mixed $offset
+     */
+    public function offsetExists($offset): bool
     {
         return isset($this->dataList[$offset]);
     }
 
+    /**
+     * @param mixed $offset
+     * @return mixed
+     */
     public function offsetGet($offset)
     {
         if (!isset($this->dataList[$offset])) {
@@ -133,7 +146,11 @@ class EntityCollection implements Collection, Iterator, Countable, ArrayAccess,
         return $this->getEntityByOffset($offset);
     }
 
-    public function offsetSet($offset, $value)
+    /**
+     * @param mixed $offset
+     * @param mixed $value
+     */
+    public function offsetSet($offset, $value): void
     {
         if (!($value instanceof Entity)) {
             throw new InvalidArgumentException('Only Entity is allowed to be added to EntityCollection.');
@@ -148,17 +165,23 @@ class EntityCollection implements Collection, Iterator, Countable, ArrayAccess,
         $this->dataList[$offset] = $value;
     }
 
+    /**
+     * @param mixed $offset
+     */
     public function offsetUnset($offset)
     {
         unset($this->dataList[$offset]);
     }
 
-    public function count()
+    public function count(): int
     {
         return count($this->dataList);
     }
 
-    public function seek($offset)
+    /**
+     * @param int $offset
+     */
+    public function seek($offset): void
     {
         $this->position = $offset;
 
@@ -167,7 +190,7 @@ class EntityCollection implements Collection, Iterator, Countable, ArrayAccess,
         }
     }
 
-    public function append(Entity $entity)
+    public function append(Entity $entity): void
     {
         $this->dataList[] = $entity;
     }
diff --git a/application/Espo/ORM/Query/Part/OrderList.php b/application/Espo/ORM/Query/Part/OrderList.php
index a1e0ac7853..fb6526f30e 100644
--- a/application/Espo/ORM/Query/Part/OrderList.php
+++ b/application/Espo/ORM/Query/Part/OrderList.php
@@ -62,40 +62,27 @@ class OrderList implements Iterator
         return new self($list);
     }
 
-    /**
-     * @return void
-     */
-    public function rewind()
+    public function rewind(): void
     {
         $this->position = 0;
     }
 
-    /**
-     * @return Order
-     */
-    public function current()
+    public function current(): Order
     {
         return $this->list[$this->position];
     }
 
-    /**
-     *
-     * @return int
-     */
-    public function key()
+    public function key(): int
     {
         return $this->position;
     }
 
-    public function next()
+    public function next(): void
     {
         ++$this->position;
     }
 
-    /**
-     * @return bool
-     */
-    public function valid()
+    public function valid(): bool
     {
         return isset($this->list[$this->position]);
     }
diff --git a/application/Espo/ORM/SthCollection.php b/application/Espo/ORM/SthCollection.php
index 9908acd4c1..96030e2c95 100644
--- a/application/Espo/ORM/SthCollection.php
+++ b/application/Espo/ORM/SthCollection.php
@@ -34,6 +34,7 @@ use Espo\ORM\QueryComposer\QueryComposer as QueryComposer;
 
 use IteratorAggregate;
 use Countable;
+use Traversable;
 use PDO;
 
 /**
@@ -103,7 +104,7 @@ class SthCollection implements Collection, IteratorAggregate, Countable
         return $this->query;
     }
 
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         return (function () {
             if (isset($this->sth)) {