diff --git a/composer.json b/composer.json
index f13013b..2c31abe 100644
--- a/composer.json
+++ b/composer.json
@@ -22,6 +22,7 @@
         "ext-intl": "*",
         "ext-json": "*",
         "ext-hash": "*",
+        "ext-filter": "*",
         "ext-dom": "*",
         "nicolus/picofeed": "^0.1.43",
         "hosteurope/password-generator": "1.*",
diff --git a/composer.lock b/composer.lock
index 28a7aa6..9f8f371 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "2a87797422ae569bafcbb6476461ac38",
+    "content-hash": "c658930fbc56b2b2cf646e34c6a8d8d3",
     "packages": [
         {
             "name": "docopt/docopt",
@@ -1353,11 +1353,12 @@
         "ext-intl": "*",
         "ext-json": "*",
         "ext-hash": "*",
+        "ext-filter": "*",
         "ext-dom": "*"
     },
     "platform-dev": [],
     "platform-overrides": {
         "php": "7.1.33"
     },
-    "plugin-api-version": "2.0.0"
+    "plugin-api-version": "2.1.0"
 }
diff --git a/docs/en/020_Getting_Started/index.md b/docs/en/020_Getting_Started/index.md
index 35b4a57..7feed47 100644
--- a/docs/en/020_Getting_Started/index.md
+++ b/docs/en/020_Getting_Started/index.md
@@ -8,13 +8,13 @@ For reference, The Arsse has the following requirements:
 
 - A Linux server running Nginx or Apache 2.4
 - PHP 7.1.0 or later with the following extensions:
-    - [intl](http://php.net/manual/en/book.intl.php), [json](http://php.net/manual/en/book.json.php), [hash](http://php.net/manual/en/book.hash.php), and [dom](http://php.net/manual/en/book.dom.php)
-    - [simplexml](http://php.net/manual/en/book.simplexml.php), and [iconv](http://php.net/manual/en/book.iconv.php)
+    - [intl](https://php.net/manual/en/book.intl.php), [json](https://php.net/manual/en/book.json.php), [hash](https://php.net/manual/en/book.hash.php), [filter](https://php.net/manual/en/book.filter.php), and [dom](https://php.net/manual/en/book.dom.php)
+    - [simplexml](https://php.net/manual/en/book.simplexml.php), and [iconv](https://php.net/manual/en/book.iconv.php)
     - One of:
-        - [sqlite3](http://php.net/manual/en/book.sqlite3.php) or [pdo_sqlite](http://php.net/manual/en/ref.pdo-sqlite.php) for SQLite databases
-        - [pgsql](http://php.net/manual/en/book.pgsql.php) or [pdo_pgsql](http://php.net/manual/en/ref.pdo-pgsql.php) for PostgreSQL 10 or later databases
-        - [mysqli](http://php.net/manual/en/book.mysqli.php) or [pdo_mysql](http://php.net/manual/en/ref.pdo-mysql.php) for MySQL/Percona 8.0.11 or later databases
-    - [curl](http://php.net/manual/en/book.curl.php) (optional)
+        - [sqlite3](https://php.net/manual/en/book.sqlite3.php) or [pdo_sqlite](https://php.net/manual/en/ref.pdo-sqlite.php) for SQLite databases
+        - [pgsql](https://php.net/manual/en/book.pgsql.php) or [pdo_pgsql](https://php.net/manual/en/ref.pdo-pgsql.php) for PostgreSQL 10 or later databases
+        - [mysqli](https://php.net/manual/en/book.mysqli.php) or [pdo_mysql](https://php.net/manual/en/ref.pdo-mysql.php) for MySQL/Percona 8.0.11 or later databases
+    - [curl](https://php.net/manual/en/book.curl.php) (optional)
 - Privileges either to create and run systemd services, or to run cron jobs
 
 Instructions for how to satisfy the PHP extension requirements for Arch Linux and Debian systems are included in the next section.