diff --git a/.github/workflows/integrationtest.yml b/.github/workflows/integrationtest.yml
index 9e19b68..dec4c35 100644
--- a/.github/workflows/integrationtest.yml
+++ b/.github/workflows/integrationtest.yml
@@ -26,11 +26,6 @@ jobs:
     strategy:
       matrix:
         php:
-          - '5.4'
-          - '5.5'
-          - '5.6'
-          - '7.0'
-          - '7.1'
           - '7.2'
           - '7.3'
           - '7.4'
@@ -43,67 +38,24 @@ jobs:
           - '8.6'
         composer:
           - 'v2'
+          - '2.2'
         os:
           - 'ubuntu-latest'
           - 'windows-latest'
 
         exclude:
-          # Installing on Windows with PHP 5.4 runs into all sorts of problems (which are not ours).
-          # Considering PHP 5.4 is ancient, I deem it acceptable to exclude the Windows PHP 5.4 builds.
-          # @link https://github.com/PHPCSStandards/composer-installer/pull/213
-          - php: '5.4'
-            os: 'windows-latest'
-
-        include:
-          # Composer 2.3 drops support for PHP < 7.2, so for PHP 5.4 to 7.1, `v2` will install
-          # Composer 2.2, for PHP 7.2 and up, `v2` will install Composer >= 2.3.
-          # These builds make sure the Composer 2.2 LTS version is 100% supported for PHP 7.2-8.3.
-          # Note: Composer 2.2 is not compatible with PHP 8.4 and it is unlikely that it will be
-          # made compatible with PHP 8.4.
-          - php: '7.2'
-            composer: '2.2'
-            os: 'ubuntu-latest'
-          - php: '7.3'
-            composer: '2.2'
-            os: 'ubuntu-latest'
-          - php: '7.4'
-            composer: '2.2'
-            os: 'ubuntu-latest'
-          - php: '8.0'
-            composer: '2.2'
-            os: 'ubuntu-latest'
-          - php: '8.1'
-            composer: '2.2'
-            os: 'ubuntu-latest'
-          - php: '8.2'
-            composer: '2.2'
-            os: 'ubuntu-latest'
-          - php: '8.3'
+          # Composer 2.3 drops support for PHP < 7.2, so `v2` will install Composer >= 2.3.
+          # The current matrix is set up to safeguard that the Composer 2.2 LTS version is 100% supported for PHP 7.2-8.3.
+          # Note: Composer 2.2 is not compatible with PHP >= 8.4 and it is unlikely that it will be
+          # made compatible with PHP >= 8.4, so we need to exclude those builds.
+          - php: '8.4'
             composer: '2.2'
-            os: 'ubuntu-latest'
-
-          - php: '7.2'
-            composer: '2.2'
-            os: 'windows-latest'
-          - php: '7.3'
+          - php: '8.5'
             composer: '2.2'
-            os: 'windows-latest'
-          - php: '7.4'
-            composer: '2.2'
-            os: 'windows-latest'
-          - php: '8.0'
+          - php: '8.6'
             composer: '2.2'
-            os: 'windows-latest'
-          - php: '8.1'
-            composer: '2.2'
-            os: 'windows-latest'
-          - php: '8.2'
-            composer: '2.2'
-            os: 'windows-latest'
-          - php: '8.3'
-            composer: '2.2'
-            os: 'windows-latest'
 
+        include:
           # Also test against the dev version of Composer for early warning about upcoming changes.
           - php: 'latest'
             composer: 'snapshot'
diff --git a/.github/workflows/phplint.yml b/.github/workflows/phplint.yml
index 3c080b2..dbc5d6c 100644
--- a/.github/workflows/phplint.yml
+++ b/.github/workflows/phplint.yml
@@ -22,7 +22,7 @@ jobs:
 
     strategy:
       matrix:
-        php: ['5.4', '5.6', '7.2', 'latest', 'nightly']
+        php: ['7.2', 'latest', 'nightly']
 
     continue-on-error: ${{ matrix.php == 'nightly' }}
 
diff --git a/.github/workflows/quicktest.yml b/.github/workflows/quicktest.yml
index 13f49aa..b840abf 100644
--- a/.github/workflows/quicktest.yml
+++ b/.github/workflows/quicktest.yml
@@ -28,28 +28,14 @@ jobs:
     strategy:
       matrix:
         php:
-          - '5.4'
           - '7.2'
           - 'latest'
         composer:
-          # Note: for PHP 5.4 - 7.1, "v2" will install Composer 2.2.
-          # For PHP 7.2+, it will install Composer "latest".
           - 'v2'
         os:
           - 'ubuntu-latest'
           - 'windows-latest'
 
-        # Installing on Windows with PHP 5.4 runs into all sorts of problems (which are not ours).
-        # Exclude the Windows PHP 5.4 builds and replace them with PHP 5.5 for the same.
-        # @link https://github.com/PHPCSStandards/composer-installer/issues/181
-        # @link https://github.com/PHPCSStandards/composer-installer/pull/213
-        exclude:
-          - php: '5.4'
-            os: 'windows-latest'
-        include:
-          - php: '5.5'
-            os: 'windows-latest'
-
     name: "Quick test"
 
     steps:
diff --git a/.github/workflows/securitycheck.yml b/.github/workflows/securitycheck.yml
index 5b09f5d..e1fa859 100644
--- a/.github/workflows/securitycheck.yml
+++ b/.github/workflows/securitycheck.yml
@@ -23,7 +23,7 @@ jobs:
 
     strategy:
       matrix:
-        php: ['5.4']
+        php: ['7.2', 'latest']
 
     steps:
       - name: Checkout code
@@ -47,12 +47,5 @@ jobs:
           # Ignore development-only packages in security check
           composer-options: "--no-dev"
 
-      - name: Download security checker
-        # yamllint disable-line rule:line-length
-        run: wget -P . https://github.com/fabpot/local-php-security-checker/releases/download/v2.0.6/local-php-security-checker_2.0.6_linux_amd64
-
-      - name: Make security checker executable
-        run: chmod +x ./local-php-security-checker_2.0.6_linux_amd64
-
       - name: Check against insecure dependencies
-        run: ./local-php-security-checker_2.0.6_linux_amd64 --path=vendor/composer/installed.json
+        run: composer audit --abandoned=fail
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index c182f5b..b7f0db4 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -41,11 +41,11 @@ These tools fall into two categories: PHP and non-PHP.
 
 The PHP specific tools used by this build are:
 
+- [Composer][] to install dependencies.
 - [PHPUnit][] and the [PHPUnit Polyfills][] for the integration tests.
 - [PHP_CodeSniffer][] to verify PHP code complies with the [PSR12][] standard.
 - [PHPCompatibility][] to verify that code is written in a PHP cross-version compatible manner.
 - [PHP-Parallel-Lint][] to check against parse errors in PHP files.
-- [PHP-Security-Checker][] to prevent insecure dependencies being installed.
 
 The automated checks with these tools are run via [GitHub Actions][].
 
@@ -54,28 +54,24 @@ run locally with PHP.
 
 For the Parallel Lint check, the `composer lint` script has been added for convenience.
 
-The Security Checker package is not included in the Composer configuration. An executable
-can be downloaded suitable for your operating system from their [releases page][].
-
 Alternatively, these tools can be run using `docker run`, through the Docker
 images provided by [Pipeline-Component][].
 
+[Composer]: https://getcomposer.org/
 [PHPUnit]: https://phpunit.de/
 [PHPUnit Polyfills]: https://github.com/Yoast/PHPUnit-Polyfills/
 [PHP_CodeSniffer]: https://github.com/PHPCSStandards/PHP_CodeSniffer
 [PHPCompatibility]: https://github.com/PHPCompatibility/PHPCompatibility
 [PHP-Parallel-Lint]: https://github.com/php-parallel-lint/PHP-Parallel-Lint
-[PHP-Security-Checker]: https://github.com/fabpot/local-php-security-checker
 [PSR12]: https://www.php-fig.org/psr/psr-12/
-[releases page]: https://github.com/fabpot/local-php-security-checker/releases/
 
 #### Automated testing
 
 This package includes a test setup for automated testing on all supported PHP versions
 using [PHPUnit][] with the [PHPUnit Polyfills][].
-This means that tests can be written for the latest version of PHPUnit
+This means that tests can be written for the highest supported version of PHPUnit
 (9.x at the time of writing) and still be run on all PHPUnit versions needed to test
-all supported PHP versions (PHPUnit 4.x - 9.x).
+all supported PHP versions (PHPUnit 8.x - 9.x).
 
 The tests can be run both via a Composer installed version of PHPUnit, as well as using
 a PHPUnit PHAR file, however, whichever way you run the tests, you will always need to
diff --git a/README.md b/README.md
index fb6851a..e954311 100644
--- a/README.md
+++ b/README.md
@@ -46,9 +46,9 @@ That's it.
 
 This plugin is compatible with:
 
-- PHP **5.4+**, **7.x**, and **8.x** (Support for PHP v8 is available since [`v0.7.0`][v0.7])
-- [Composer][composer] **2.2+** (Support for Composer v2 is available since [`v0.7.0`][v0.7]; support for Composer < 2.2 was dropped in [`v1.1.0`][v1.1])
-- [PHP_CodeSniffer][codesniffer] **3.x** and **4.x**(Support for PHP_CodeSniffer v4 is available since [`v0.7.0`][v0.7], support for PHP_CodeSniffer v2 was dropped in [`v1.2.0`][v1.2])
+- PHP **7.2**, and **8.x** _(Support for PHP v8 is available since [`v0.7.0`][v0.7], support for PHP < 7.2 was dropped in [`v1.3.0`][v1.3])_
+- [Composer][composer] **2.2+** _(Support for Composer v2 is available since [`v0.7.0`][v0.7]; support for Composer < 2.2 was dropped in [`v1.1.0`][v1.1])_
+- [PHP_CodeSniffer][codesniffer] **3.x** and **4.x** _(Support for PHP_CodeSniffer v4 is available since [`v0.7.0`][v0.7], support for PHP_CodeSniffer v2 was dropped in [`v1.2.0`][v1.2])_
 
 ### How it works
 
@@ -162,8 +162,8 @@ Create a composer package of your coding standard by adding a `composer.json` fi
   "name" : "acme/phpcodesniffer-our-standards",
   "description" : "Package contains all coding standards of the Acme company",
   "require" : {
-    "php" : ">=5.4.0",
-    "squizlabs/php_codesniffer" : "^3.13"
+    "php" : ">=7.2.0",
+    "squizlabs/php_codesniffer" : "^4.0"
   },
   "type" : "phpcodesniffer-standard"
 }
@@ -276,3 +276,4 @@ THE SOFTWARE.
 [v0.7]: https://github.com/PHPCSStandards/composer-installer/releases/tag/v0.7.0
 [v1.1]: https://github.com/PHPCSStandards/composer-installer/releases/tag/v1.1.0
 [v1.2]: https://github.com/PHPCSStandards/composer-installer/releases/tag/v1.2.0
+[v1.3]: https://github.com/PHPCSStandards/composer-installer/releases/tag/v1.3.0
diff --git a/composer.json b/composer.json
index ba3fbff..f88b45f 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,7 @@
     "security": "https://github.com/PHPCSStandards/composer-installer/security/policy"
   },
   "require": {
-    "php": ">=5.4",
+    "php": ">=7.2",
     "composer-plugin-api": "^2.2",
     "squizlabs/php_codesniffer": "^3.1.0 || ^4.0"
   },
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index 3872638..f1fa8f6 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -14,13 +14,9 @@
     <exclude-pattern>*/vendor/*</exclude-pattern>
 
     <rule ref="PHPCompatibility"/>
-    <config name="testVersion" value="5.4-"/>
+    <config name="testVersion" value="7.2-"/>
 
-    <rule ref="PSR12">
-        <!-- Constant visibility can not be declared (yet) as the minimum supported PHP version is 5.4
-             and constant visibility was only introduced in PHP 7.1. -->
-        <exclude name="PSR12.Properties.ConstantVisibility.NotFound"/>
-    </rule>
+    <rule ref="PSR12"/>
 
     <rule ref="Generic.Formatting.MultipleStatementAlignment">
         <properties>
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index d71e506..cc59987 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/7.5/phpunit.xsd"
+    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.2/phpunit.xsd"
     backupGlobals="false"
     bootstrap="./tests/bootstrap.php"
     beStrictAboutTestsThatDoNotTestAnything="true"
diff --git a/src/Plugin.php b/src/Plugin.php
index 03f9b54..eabff1e 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -34,23 +34,23 @@
  */
 class Plugin implements PluginInterface, EventSubscriberInterface
 {
-    const KEY_MAX_DEPTH = 'phpcodesniffer-search-depth';
+    public const KEY_MAX_DEPTH = 'phpcodesniffer-search-depth';
 
-    const MESSAGE_ERROR_WRONG_MAX_DEPTH =
+    public const MESSAGE_ERROR_WRONG_MAX_DEPTH =
         'The value of "%s" (in the composer.json "extra".section) must be an integer larger than %d, %s given.';
 
-    const MESSAGE_NOT_INSTALLED      = 'PHPCodeSniffer is not installed';
-    const MESSAGE_NOTHING_TO_INSTALL = 'No PHPCS standards to install or update';
-    const MESSAGE_PLUGIN_UNINSTALLED = 'PHPCodeSniffer Composer Installer is uninstalled';
-    const MESSAGE_RUNNING_INSTALLER  = 'Running PHPCodeSniffer Composer Installer';
+    public const MESSAGE_NOT_INSTALLED      = 'PHPCodeSniffer is not installed';
+    public const MESSAGE_NOTHING_TO_INSTALL = 'No PHPCS standards to install or update';
+    public const MESSAGE_PLUGIN_UNINSTALLED = 'PHPCodeSniffer Composer Installer is uninstalled';
+    public const MESSAGE_RUNNING_INSTALLER  = 'Running PHPCodeSniffer Composer Installer';
 
-    const PACKAGE_NAME = 'squizlabs/php_codesniffer';
-    const PACKAGE_TYPE = 'phpcodesniffer-standard';
+    public const PACKAGE_NAME = 'squizlabs/php_codesniffer';
+    public const PACKAGE_TYPE = 'phpcodesniffer-standard';
 
-    const PHPCS_CONFIG_REGEX = '`%s:[^\r\n]+`';
-    const PHPCS_CONFIG_KEY   = 'installed_paths';
+    public const PHPCS_CONFIG_REGEX = '`%s:[^\r\n]+`';
+    public const PHPCS_CONFIG_KEY   = 'installed_paths';
 
-    const PLUGIN_NAME = 'dealerdirect/phpcodesniffer-composer-installer';
+    public const PLUGIN_NAME = 'dealerdirect/phpcodesniffer-composer-installer';
 
     /**
      * @var Composer
diff --git a/tests/CreateComposerZipArtifacts.php b/tests/CreateComposerZipArtifacts.php
index 3387378..98537a3 100644
--- a/tests/CreateComposerZipArtifacts.php
+++ b/tests/CreateComposerZipArtifacts.php
@@ -34,7 +34,7 @@ class CreateComposerZipArtifacts
      *
      * @var string
      */
-    const FIXTURE_VERSION = '1.0.0';
+    private const FIXTURE_VERSION = '1.0.0';
 
     /**
      * The full path to the directory to place the zipped artifacts in (including trailing slash).
diff --git a/tests/PHPCSVersions.php b/tests/PHPCSVersions.php
index c84f5df..d7ca118 100644
--- a/tests/PHPCSVersions.php
+++ b/tests/PHPCSVersions.php
@@ -22,14 +22,14 @@ final class PHPCSVersions
      *
      * @var string
      */
-    const MASTER = '4.x-dev';
+    private const MASTER = '4.x-dev';
 
     /**
      * Composer name for the development branch for the next major.
      *
      * @var string
      */
-    const NEXT_MAJOR = '5.x-dev as 4.99.99';
+    private const NEXT_MAJOR = '5.x-dev as 4.99.99';
 
     /**
      * List of all PHPCS version which are supported by this plugin.
@@ -334,20 +334,6 @@ public static function getSupportedVersions()
          * Adjust the list of available versions based on the PHP version on which the tests are run.
          */
         switch (\CLI_PHP_MINOR) {
-            case '5.4':
-            case '5.5':
-            case '5.6':
-            case '7.0':
-            case '7.1':
-                $versions = array_filter(
-                    self::$allPhpcsVersions,
-                    static function ($version) {
-                        // PHPCS 3.x is the last version still supporting PHP < 7.2.
-                        return version_compare($version, '3.99.99', '<=');
-                    }
-                );
-                break;
-
             case '7.2':
                 $versions = self::$allPhpcsVersions;
                 break;
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 7147fd4..048f19e 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -29,7 +29,7 @@ abstract class TestCase extends PolyfillTestCase
     public static function createTestEnvironment()
     {
         // Make temp directory
-        $class           = substr(strrchr(get_called_class(), '\\'), 1);
+        $class           = substr(strrchr(static::class, '\\'), 1);
         static::$tempDir = sys_get_temp_dir() . '/PHPCSPluginTest/' . uniqid("{$class}_", true);
 
         $subDirs = array(
@@ -340,7 +340,7 @@ protected static function stabilizeCommand($command, $workingDir = null)
 
         /*
          * If the command will be run on Windows in combination with PHP < 8.0, wrap it in an extra set of quotes.
-         * Note: it is unclear what changes in PHP 8.0, but the quotes will now suddenly break things.
+         * Note: it is unclear what changed in PHP 8.0, but the quotes will now suddenly break things.
          * Ref: https://www.php.net/manual/en/function.proc-open.php#example-3331
          */
         if (static::onWindows() === true && substr(\CLI_PHP_MINOR, 0, 1) < 8) {
diff --git a/tests/fixtures/dummy-src/composer.json b/tests/fixtures/dummy-src/composer.json
index 9ded9e2..648317f 100644
--- a/tests/fixtures/dummy-src/composer.json
+++ b/tests/fixtures/dummy-src/composer.json
@@ -4,7 +4,7 @@
     "type" : "phpcodesniffer-standard",
     "license" : "MIT",
     "require" : {
-        "php" : ">=5.4",
+        "php" : ">=7.2",
         "squizlabs/php_codesniffer" : "*",
         "dealerdirect/phpcodesniffer-composer-installer" : "*"
     },
diff --git a/tests/fixtures/dummy-subdir/composer.json b/tests/fixtures/dummy-subdir/composer.json
index 8d08236..c4745bb 100644
--- a/tests/fixtures/dummy-subdir/composer.json
+++ b/tests/fixtures/dummy-subdir/composer.json
@@ -4,7 +4,7 @@
     "type" : "phpcodesniffer-standard",
     "license" : "MIT",
     "require" : {
-        "php" : ">=5.4",
+        "php" : ">=7.2",
         "squizlabs/php_codesniffer" : "*"
     }
 }
diff --git a/tests/fixtures/incorrect-type/composer.json b/tests/fixtures/incorrect-type/composer.json
index cbc76e3..f215df5 100644
--- a/tests/fixtures/incorrect-type/composer.json
+++ b/tests/fixtures/incorrect-type/composer.json
@@ -4,7 +4,7 @@
     "type" : "coding-standard",
     "license" : "MIT",
     "require" : {
-        "php" : ">=5.4",
+        "php" : ">=7.2",
         "squizlabs/php_codesniffer" : "*",
         "dealerdirect/phpcodesniffer-composer-installer" : "*"
     },