diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index ec27b54..fc1f015 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -17,13 +17,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: ['5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0']
+        php: ['7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1']
         os: ['ubuntu-latest']
-        include:
-          - php: '5.6'
-            allow_failure: true
-          - php: '7.0'
-            allow_failure: true
 
     steps:
       - name: Checkout code base
@@ -51,20 +46,18 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     env:
-      phpunit-version: 8.5.15
+      phpunit-version: 8.5
 
     strategy:
       fail-fast: false
       matrix:
-        php: ['5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0']
+        php: ['7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1']
         os: ['ubuntu-latest']
         include:
-          - php: '5.6'
-            phpunit-version: 5.7.27
           - php: '7.0'
-            phpunit-version: 6.5.14
+            phpunit-version: 6.5
           - php: '7.1'
-            phpunit-version: 7.5.20
+            phpunit-version: 7.5
 
     steps:
       - name: Checkout code base
diff --git a/README.md b/README.md
index 5546770..e91a270 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Icinga PHP Library - Standard Library
 
-[![PHP Support](https://img.shields.io/badge/php-%3E%3D%205.6-777BB4?logo=PHP)](https://php.net/)
+[![PHP Support](https://img.shields.io/badge/php-%3E%3D%207.0-777BB4?logo=PHP)](https://php.net/)
 ![Build Status](https://github.com/Icinga/ipl-stdlib/workflows/PHP%20Tests/badge.svg?branch=master)
 
 This is the Stdlib prototype for the Icinga PHP library ([ipl](https://github.com/Icinga/ipl)).
diff --git a/composer.json b/composer.json
index ebc12b6..8e6b304 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
     "type": "library",
     "license": "MIT",
     "autoload": {
-        "files": ["src/functions_include.php", "src/polyfill-php71.php", "src/polyfill-php70.php"],
+        "files": ["src/functions_include.php", "src/polyfill-php71.php"],
         "psr-4": {
             "ipl\\Stdlib\\": "src"
         }
@@ -15,7 +15,7 @@
         }
     },
     "require": {
-        "php": ">=5.6.0",
+        "php": ">=7.0",
         "ext-openssl": "*",
         "evenement/evenement": "^2"
     }
diff --git a/src/BaseFilter.php b/src/BaseFilter.php
new file mode 100644
index 0000000..267decb
--- /dev/null
+++ b/src/BaseFilter.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace ipl\Stdlib;
+
+use ipl\Stdlib\Filter\Rule;
+
+trait BaseFilter
+{
+    /** @var Rule Base filter */
+    private $baseFilter;
+
+    /**
+     * Get whether a base filter has been set
+     *
+     * @return bool
+     */
+    public function hasBaseFilter(): bool
+    {
+        return $this->baseFilter !== null;
+    }
+
+    /**
+     * Get the base filter
+     *
+     * @return ?Rule
+     */
+    public function getBaseFilter()
+    {
+        return $this->baseFilter;
+    }
+
+    /**
+     * Set the base filter
+     *
+     * @param Rule $baseFilter
+     *
+     * @return $this
+     */
+    public function setBaseFilter(Rule $baseFilter = null): self
+    {
+        $this->baseFilter = $baseFilter;
+
+        return $this;
+    }
+}
diff --git a/src/polyfill-php70.php b/src/polyfill-php70.php
deleted file mode 100644
index 54c1771..0000000
--- a/src/polyfill-php70.php
+++ /dev/null
@@ -1,22 +0,0 @@
-<?php
-
-if (PHP_VERSION_ID < 70000 && ! function_exists('\random_bytes')) {
-    /**
-     * Generates cryptographically secure pseudo-random bytes
-     *
-     * @param int $length The length of the random string that should be returned in bytes.
-     *
-     * @return string Returns a string containing the requested number of cryptographically secure random bytes.
-     *
-     * @throws Exception if it was not possible to gather sufficient entropy.
-     */
-    function random_bytes($length)
-    {
-        $bytes = openssl_random_pseudo_bytes($length, $strong);
-        if (! $strong) {
-            throw new Exception('Unable to generate a cryptographically strong result');
-        }
-
-        return $bytes;
-    }
-}