diff --git a/phpBB/phpbb/di/service_collection.php b/phpBB/phpbb/di/service_collection.php
index 3a18644891..a8eeeab8bb 100644
--- a/phpBB/phpbb/di/service_collection.php
+++ b/phpBB/phpbb/di/service_collection.php
@@ -20,6 +20,11 @@ use Symfony\Component\DependencyInjection\ContainerInterface;
 */
 class service_collection extends \ArrayObject
 {
+	/**
+	* @var \Symfony\Component\DependencyInjection\ContainerInterface
+	*/
+	protected $container;
+
 	/**
 	* Constructor
 	*
@@ -30,6 +35,44 @@ class service_collection extends \ArrayObject
 		$this->container = $container;
 	}
 
+	/**
+	* {@inheritdoc}
+	*/
+	public function getIterator()
+	{
+		return new service_collection_iterator($this->container, $this);
+	}
+
+	// Because of a PHP issue we have to redefine offsetExists
+	// (even with a call to the parent):
+	// 		https://bugs.php.net/bug.php?id=66834
+	// 		https://bugs.php.net/bug.php?id=67067
+	// But it triggers a sniffer issue that we have to skip
+	// @codingStandardsIgnoreStart
+	/**
+	* {@inheritdoc}
+	*/
+	public function offsetExists($index)
+	{
+		return parent::offsetExists($index);
+	}
+	// @codingStandardsIgnoreEnd
+
+	/**
+	* {@inheritdoc}
+	*/
+	public function offsetGet($index)
+	{
+		$task = parent::offsetGet($index);
+		if ($task === null)
+		{
+			$task = $this->container->get($index);
+			$this->offsetSet($index, $task);
+		}
+
+		return $task;
+	}
+
 	/**
 	* Add a service to the collection
 	*
@@ -38,8 +81,6 @@ class service_collection extends \ArrayObject
 	*/
 	public function add($name)
 	{
-		$task = $this->container->get($name);
-
-		$this->offsetSet($name, $task);
+		$this->offsetSet($name, null);
 	}
 }
diff --git a/phpBB/phpbb/di/service_collection_iterator.php b/phpBB/phpbb/di/service_collection_iterator.php
new file mode 100644
index 0000000000..54aefca1f7
--- /dev/null
+++ b/phpBB/phpbb/di/service_collection_iterator.php
@@ -0,0 +1,87 @@
+<?php
+/**
+*
+* This file is part of the phpBB Forum Software package.
+*
+* @copyright (c) phpBB Limited <https://www.phpbb.com>
+* @license GNU General Public License, version 2 (GPL-2.0)
+*
+* For full copyright and license information, please see
+* the docs/CREDITS.txt file.
+*
+*/
+
+namespace phpbb\di;
+
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+* Iterator which loads the services when they are requested
+*/
+class service_collection_iterator extends \ArrayIterator
+{
+	/**
+	* @var \Symfony\Component\DependencyInjection\ContainerInterface
+	*/
+	protected $container;
+
+	/**
+	* Construct an ArrayIterator for service_collection
+	*
+	* @param ContainerInterface $container Container object
+	* @param array $array The array or object to be iterated on.
+	* @param int $flags Flags to control the behaviour of the ArrayObject object.
+	* @see ArrayObject::setFlags()
+	*/
+	public function __construct(ContainerInterface $container, $array = array(), $flags = 0)
+	{
+		parent::__construct($array, $flags);
+		$this->container = $container;
+	}
+
+	/**
+	* {@inheritdoc}
+	*/
+	public function offsetGet($index)
+	{
+		$task = parent::offsetGet($index);
+		if ($task === null)
+		{
+			$task = $this->container->get($index);
+			$this->offsetSet($index, $task);
+		}
+
+		return $task;
+	}
+
+	// Because of a PHP issue we have to redefine offsetExists
+	// (even with a call to the parent):
+	// 		https://bugs.php.net/bug.php?id=66834
+	// 		https://bugs.php.net/bug.php?id=67067
+	// But it triggers a sniffer issue that we have to skip
+	// @codingStandardsIgnoreStart
+	/**
+	* {@inheritdoc}
+	*/
+	public function offsetExists($index)
+	{
+		parent::offsetExists($index);
+	}
+	// @codingStandardsIgnoreEnd
+
+	/**
+	* {@inheritdoc}
+	*/
+	public function current()
+	{
+		$task = parent::current();
+		if ($task === null)
+		{
+			$name = $this->key();
+			$task = $this->container->get($name);
+			$this->offsetSet($name, $task);
+		}
+
+		return $task;
+	}
+}