diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 263b5ab..ca9950d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,7 +20,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: ["7.4", "8.0", "8.1", "8.2"]
+        php-version: ["7.4", "8.0", "8.1", "8.2", "8.3", "8.4"]
     steps:
       - uses: actions/checkout@v3
       - name: Installing PHP ${{ matrix.php-version }}
diff --git a/README.md b/README.md
index 77b2d05..bb435f0 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@
 
 NBBC is a high-speed, extensible, easy-to-use validating BBCode parser that accepts BBCode as input and generates XHTML 1.0 Transitional-compliant markup as its output no matter how mangled the input. It includes built-in support for most common BBCode, as well as external-wiki support, image-library support, a standard library of smileys (emoticons), and via its powerful API it can even be transformed into a validating HTML parser!
 
-NBBC is well-tested, with its output validated against a unit-test suite with over a hundred different tests. It is written entirely in PHP, using clean, namespace-friendly, object-oriented code, and it is compatible both PHP 5.4 and up.
+NBBC is well-tested, with its output validated against a unit-test suite with over a hundred different tests. It is written entirely in PHP, using clean, namespace-friendly, object-oriented code, and it is compatible with PHP 7.1 and up.
 
 While flexible and powerful, NBBC is also designed to be an easy to use, and is an easy drop-in replacement for most existing BBCode-parsing solutions. In many cases, it can be implemented in your own projects with only two or three lines of code. Only a single PHP source file is necessary in your projects, a compact, optimized file that is automatically generated from the included heavily-commented original PHP source files.
 
diff --git a/composer.json b/composer.json
index b3cf391..1de5281 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,7 @@
 		}
 	],
 	"require": {
-		"php": ">=5.4.0"
+		"php": ">=7.1.0"
 	},
 	"require-dev": {
 		"phpunit/phpunit": "~8"
diff --git a/doc/install_req.html b/doc/install_req.html
index 4f6ce57..a4b15b4 100644
--- a/doc/install_req.html
+++ b/doc/install_req.html
@@ -21,7 +21,7 @@ <h3>A. Requirements</h3>
 <p>To use NBBC in your programs, you will need to have the following:</p>
 
 <ul>
-<li>A web server running PHP 4.0.5 or higher, or PHP 5.0 or higher.</li>
+<li>A web server running PHP 7.1 or higher.</li>
 <li>Some PHP programming skills (say, skill level 2, where 1 is "newbie" and 5 is "guru").</li>
 </ul>
 
diff --git a/doc/intro_over.html b/doc/intro_over.html
index ce7488b..29bce66 100644
--- a/doc/intro_over.html
+++ b/doc/intro_over.html
@@ -24,7 +24,7 @@ <h1><img src='nbbc-small.png' width='206' height='56' alt='NBBC' /><br />The New
 Copyright &copy; 2008-10, the Phantom Inker.  All rights reserved.</p>
 
 <p>The New BBCode Parser (NBBC) is a fully-validating, high-speed, extensible parser
-for the BBCode document language, written in PHP, compatible with PHP 4.0.5+ and PHP 5.
+for the BBCode document language, written in PHP, compatible with PHP 7.1+.
 It converts BBCode input into HTML output, and can guarantee that the output will be
 fully conformant to the XHTML 1.0 Strict standard no matter how badly-mangled the BBCode
 input is.</p>
diff --git a/doc/src/install_req.tpl b/doc/src/install_req.tpl
index 3f5f1b7..175cadf 100644
--- a/doc/src/install_req.tpl
+++ b/doc/src/install_req.tpl
@@ -2,7 +2,7 @@
 <p>To use NBBC in your programs, you will need to have the following:</p>
 
 <ul>
-<li>A web server running PHP 4.0.5 or higher, or PHP 5.0 or higher.</li>
+<li>A web server running PHP 7.1 or higher.</li>
 <li>Some PHP programming skills (say, skill level 2, where 1 is "newbie" and 5 is "guru").</li>
 </ul>
 
diff --git a/doc/src/intro_over.tpl b/doc/src/intro_over.tpl
index e4bc998..8087057 100644
--- a/doc/src/intro_over.tpl
+++ b/doc/src/intro_over.tpl
@@ -5,7 +5,7 @@
 Copyright &copy; 2008-10, the Phantom Inker.  All rights reserved.</p>
 
 <p>The New BBCode Parser (NBBC) is a fully-validating, high-speed, extensible parser
-for the BBCode document language, written in PHP, compatible with PHP 4.0.5+ and PHP 5.
+for the BBCode document language, written in PHP, compatible with PHP 7.1+.
 It converts BBCode input into HTML output, and can guarantee that the output will be
 fully conformant to the XHTML 1.0 Strict standard no matter how badly-mangled the BBCode
 input is.</p>
diff --git a/src/BBCode.php b/src/BBCode.php
index ad6f553..bf199b2 100644
--- a/src/BBCode.php
+++ b/src/BBCode.php
@@ -229,7 +229,7 @@ class BBCode {
      *
      * @param BBCodeLibrary|null $library
      */
-    public function __construct(BBCodeLibrary $library = null) {
+    public function __construct(?BBCodeLibrary $library = null) {
         $this->defaults = isset($library) ? $library : new BBCodeLibrary();
         $this->tag_rules = $this->defaults->default_tag_rules;
         $this->smileys = $this->defaults->default_smileys;