diff --git a/composer.json b/composer.json
index 36a6f74..99c26a9 100644
--- a/composer.json
+++ b/composer.json
@@ -4,8 +4,11 @@
 	"type": "project",
 	"license": "GPL-2.0-or-later",
 	"require-dev": {
-		"phpunit/phpunit": "^12.5",
 		"php-stubs/wordpress-stubs": "^6.8",
+		"phpcompatibility/php-compatibility": "^10.0@alpha",
+		"phpcompatibility/phpcompatibility-paragonie": "^2.0@alpha",
+		"phpcompatibility/phpcompatibility-wp": "^3.0@alpha",
+		"phpunit/phpunit": "^12.5",
 		"sirbrillig/phpcs-changed": "^2.11",
 		"vimeo/psalm": "^6.0",
 		"wp-coding-standards/wpcs": "^3.0"
diff --git a/composer.lock b/composer.lock
index 4c98970..b698b8f 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": "175cfcb93fa1b19f22942ab74fba5cb1",
+    "content-hash": "92c4c00406d0bfcc7057aaa5f9b93e3b",
     "packages": [
         {
             "name": "citation-style-language/locales",
@@ -2244,6 +2244,234 @@
             },
             "time": "2026-02-03T19:29:21+00:00"
         },
+        {
+            "name": "phpcompatibility/php-compatibility",
+            "version": "10.0.0-alpha2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/PHPCompatibility/PHPCompatibility.git",
+                "reference": "e0f0e5a3dc819a4a0f8d679a0f2453d941976e18"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/PHPCompatibility/PHPCompatibility/zipball/e0f0e5a3dc819a4a0f8d679a0f2453d941976e18",
+                "reference": "e0f0e5a3dc819a4a0f8d679a0f2453d941976e18",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.4",
+                "phpcsstandards/phpcsutils": "^1.1.2",
+                "squizlabs/php_codesniffer": "^3.13.3 || ^4.0"
+            },
+            "replace": {
+                "wimg/php-compatibility": "*"
+            },
+            "require-dev": {
+                "php-parallel-lint/php-console-highlighter": "^1.0.0",
+                "php-parallel-lint/php-parallel-lint": "^1.4.0",
+                "phpcsstandards/phpcsdevcs": "^1.2.0",
+                "phpcsstandards/phpcsdevtools": "^1.2.3",
+                "phpunit/phpunit": "^4.8.36 || ^5.7.21 || ^6.0 || ^7.0 || ^8.0 || ^9.3.4 || ^10.5.32 || ^11.3.3",
+                "yoast/phpunit-polyfills": "^1.1.5 || ^2.0.5 || ^3.1.0"
+            },
+            "type": "phpcodesniffer-standard",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "9.x-dev",
+                    "dev-develop": "10.x-dev"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "LGPL-3.0-or-later"
+            ],
+            "authors": [
+                {
+                    "name": "Wim Godden",
+                    "homepage": "https://github.com/wimg",
+                    "role": "lead"
+                },
+                {
+                    "name": "Juliette Reinders Folmer",
+                    "homepage": "https://github.com/jrfnl",
+                    "role": "lead"
+                },
+                {
+                    "name": "Contributors",
+                    "homepage": "https://github.com/PHPCompatibility/PHPCompatibility/graphs/contributors"
+                }
+            ],
+            "description": "A set of sniffs for PHP_CodeSniffer that checks for PHP cross-version compatibility.",
+            "homepage": "https://techblog.wimgodden.be/tag/codesniffer/",
+            "keywords": [
+                "compatibility",
+                "phpcs",
+                "standards",
+                "static analysis"
+            ],
+            "support": {
+                "issues": "https://github.com/PHPCompatibility/PHPCompatibility/issues",
+                "security": "https://github.com/PHPCompatibility/PHPCompatibility/security/policy",
+                "source": "https://github.com/PHPCompatibility/PHPCompatibility"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/PHPCompatibility",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/jrfnl",
+                    "type": "github"
+                },
+                {
+                    "url": "https://opencollective.com/php_codesniffer",
+                    "type": "open_collective"
+                },
+                {
+                    "url": "https://thanks.dev/u/gh/phpcompatibility",
+                    "type": "thanks_dev"
+                }
+            ],
+            "time": "2025-11-28T11:36:33+00:00"
+        },
+        {
+            "name": "phpcompatibility/phpcompatibility-paragonie",
+            "version": "2.0.0-alpha2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/PHPCompatibility/PHPCompatibilityParagonie.git",
+                "reference": "7a979711c87d8202b52f56c56bd719d09d8ed7f5"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/PHPCompatibility/PHPCompatibilityParagonie/zipball/7a979711c87d8202b52f56c56bd719d09d8ed7f5",
+                "reference": "7a979711c87d8202b52f56c56bd719d09d8ed7f5",
+                "shasum": ""
+            },
+            "require": {
+                "phpcompatibility/php-compatibility": "^10.0@dev"
+            },
+            "require-dev": {
+                "paragonie/random_compat": "dev-master",
+                "paragonie/sodium_compat": "dev-master"
+            },
+            "type": "phpcodesniffer-standard",
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "LGPL-3.0-or-later"
+            ],
+            "authors": [
+                {
+                    "name": "Wim Godden",
+                    "role": "lead"
+                },
+                {
+                    "name": "Juliette Reinders Folmer",
+                    "role": "lead"
+                }
+            ],
+            "description": "A set of rulesets for PHP_CodeSniffer to check for PHP cross-version compatibility issues in projects, while accounting for polyfills provided by the Paragonie polyfill libraries.",
+            "homepage": "http://phpcompatibility.com/",
+            "keywords": [
+                "compatibility",
+                "paragonie",
+                "phpcs",
+                "polyfill",
+                "standards",
+                "static analysis"
+            ],
+            "support": {
+                "issues": "https://github.com/PHPCompatibility/PHPCompatibilityParagonie/issues",
+                "security": "https://github.com/PHPCompatibility/PHPCompatibilityParagonie/security/policy",
+                "source": "https://github.com/PHPCompatibility/PHPCompatibilityParagonie"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/PHPCompatibility",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/jrfnl",
+                    "type": "github"
+                },
+                {
+                    "url": "https://opencollective.com/php_codesniffer",
+                    "type": "open_collective"
+                },
+                {
+                    "url": "https://thanks.dev/u/gh/phpcompatibility",
+                    "type": "thanks_dev"
+                }
+            ],
+            "time": "2025-11-29T13:09:49+00:00"
+        },
+        {
+            "name": "phpcompatibility/phpcompatibility-wp",
+            "version": "3.0.0-alpha2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/PHPCompatibility/PHPCompatibilityWP.git",
+                "reference": "bd53f24e7528422ac51d64dc8d53e8d4c4a877b3"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/PHPCompatibility/PHPCompatibilityWP/zipball/bd53f24e7528422ac51d64dc8d53e8d4c4a877b3",
+                "reference": "bd53f24e7528422ac51d64dc8d53e8d4c4a877b3",
+                "shasum": ""
+            },
+            "require": {
+                "phpcompatibility/php-compatibility": "^10.0@dev",
+                "phpcompatibility/phpcompatibility-paragonie": "^2.0@dev"
+            },
+            "type": "phpcodesniffer-standard",
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "LGPL-3.0-or-later"
+            ],
+            "authors": [
+                {
+                    "name": "Wim Godden",
+                    "role": "lead"
+                },
+                {
+                    "name": "Juliette Reinders Folmer",
+                    "role": "lead"
+                }
+            ],
+            "description": "A ruleset for PHP_CodeSniffer to check for PHP cross-version compatibility issues in projects, while accounting for polyfills provided by WordPress.",
+            "homepage": "http://phpcompatibility.com/",
+            "keywords": [
+                "compatibility",
+                "phpcs",
+                "standards",
+                "static analysis",
+                "wordpress"
+            ],
+            "support": {
+                "issues": "https://github.com/PHPCompatibility/PHPCompatibilityWP/issues",
+                "security": "https://github.com/PHPCompatibility/PHPCompatibilityWP/security/policy",
+                "source": "https://github.com/PHPCompatibility/PHPCompatibilityWP"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/PHPCompatibility",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/jrfnl",
+                    "type": "github"
+                },
+                {
+                    "url": "https://opencollective.com/php_codesniffer",
+                    "type": "open_collective"
+                },
+                {
+                    "url": "https://thanks.dev/u/gh/phpcompatibility",
+                    "type": "thanks_dev"
+                }
+            ],
+            "time": "2025-12-16T13:35:20+00:00"
+        },
         {
             "name": "phpcsstandards/phpcsextra",
             "version": "1.5.1",
@@ -5637,7 +5865,11 @@
     ],
     "aliases": [],
     "minimum-stability": "stable",
-    "stability-flags": {},
+    "stability-flags": {
+        "phpcompatibility/php-compatibility": 15,
+        "phpcompatibility/phpcompatibility-paragonie": 15,
+        "phpcompatibility/phpcompatibility-wp": 15
+    },
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {},
@@ -5645,5 +5877,5 @@
     "platform-overrides": {
         "php": "8.3.30"
     },
-    "plugin-api-version": "2.9.0"
+    "plugin-api-version": "2.6.0"
 }
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index 721cd9b..f0aaf2e 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -23,6 +23,14 @@
 	<!-- Allow uppercase constants (WP conventions use globals) -->
 	<rule ref="WordPress.WP.GlobalVariablesOverride"/>
 
+	<!-- PHP version compatibility. The plugin header declares Requires PHP: 7.4, so
+	     code must not use PHP 8-only syntax or functions. PHPCompatibilityWP knows
+	     which newer functions WordPress itself polyfills (str_contains() and
+	     friends) and allows those. The 10.x line is still alpha but is the only
+	     one that knows PHP 8 syntax; 9.3.5 checks nothing past PHP 7.4. -->
+	<config name="testVersion" value="7.4-"/>
+	<rule ref="PHPCompatibilityWP"/>
+
 	<!-- Line length -->
 	<rule ref="Generic.Files.LineLength">
 		<properties>