diff --git a/CHANGELOG.md b/CHANGELOG.md
index 16c15e5..3df611d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,39 +8,70 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 [Unreleased]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/compare/v1.3.0...HEAD
 
+## [1.3.1] - 2021-08-13
+
+### Added
+
+- Extend by the Code Climate output format [#50] from [@lukas9393]. 
+
+### Fixed
+
+- PHP 8.1: silence the deprecation notices about missing return types [#64] from [@jrfnl].
+
+### Internal
+
+- Reformat changelog to use reflinks in changelog entries [#58] from [@glensc].
+
+[1.3.1]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/compare/v1.3.0...1.3.1
+
+[#50]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/50
+[#58]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/58
+[#64]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/64
+
 ## [1.3.0] - 2021-04-07
 
 ### Added
 
-- Allow for multi-part file extensions to be passed using -e (like `-e php,php.dist`) from [@jrfnl](https://github.com/jrfnl).
-- Added syntax error callback [#30](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/30) from [@arxeiss](https://github.com/arxeiss).
-- Ignore PHP startup errors [#34](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/34) from [@jrfnl](https://github.com/jrfnl).
-- Restore php 5.3 support [#51](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/51) from [@glensc](https://github.com/glensc).
+- Allow for multi-part file extensions to be passed using -e (like `-e php,php.dist`) from [@jrfnl].
+- Added syntax error callback [#30] from [@arxeiss].
+- Ignore PHP startup errors [#34] from [@jrfnl].
+- Restore php 5.3 support [#51] from [@glensc].
 
 ### Fixed
 
-- Determine skip lint process failure by status code instead of stderr content [#48](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/48) from [@jankonas](https://github.com/jankonas).
+- Determine skip lint process failure by status code instead of stderr content [#48] from [@jankonas].
 
 ### Changed
 
-- Improve wording in the readme [#52](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/52) from [@glensc](https://github.com/glensc).
+- Improve wording in the readme [#52] from [@glensc].
 
 ### Internal
 
-- Normalized composer.json from [@OndraM](https://github.com/OndraM).
-- Updated PHPCS dependency from [@jrfnl](https://github.com/jrfnl).
-- Cleaned coding style from [@jrfnl](https://github.com/jrfnl).
-- Provide one true way to run the test suite [#37](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/37) from [@mfn](https://github.com/mfn).
-- Travis: add build against PHP 8.0 and fix failing test [#41](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/41) from [@jrfnl](https://github.com/jrfnl).
-- GitHub Actions for testing, and automatic phar creation [#46](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/46) from [@roelofr](https://github.com/roelofr).
-- Add .github folder to .gitattributes export-ignore [#54](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/54) from [@glensc](https://github.com/glensc).
-- Suggest to curl composer install via HTTPS [#53](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/53) from [@reedy](https://github.com/reedy).
-- GH Actions: allow for manually triggering a workflow [#55](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/55) from [@jrfnl](https://github.com/jrfnl).
-- GH Actions: fix phar creation [#55](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/55) from [@jrfnl](https://github.com/jrfnl).
-- GH Actions: run the tests against all supported PHP versions [#55](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/55) from [@jrfnl](https://github.com/jrfnl).
-- GH Actions: report CS violations in the PR [#55](https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/55) from [@jrfnl](https://github.com/jrfnl).
+- Normalized composer.json from [@OndraM].
+- Updated PHPCS dependency from [@jrfnl].
+- Cleaned coding style from [@jrfnl].
+- Provide one true way to run the test suite [#37] from [@mfn].
+- Travis: add build against PHP 8.0 and fix failing test [#41] from [@jrfnl].
+- GitHub Actions for testing, and automatic phar creation [#46] from [@roelofr].
+- Add .github folder to .gitattributes export-ignore [#54] from [@glensc].
+- Suggest to curl composer install via HTTPS [#53] from [@reedy].
+- GH Actions: allow for manually triggering a workflow [#55] from [@jrfnl].
+- GH Actions: fix phar creation [#55] from [@jrfnl].
+- GH Actions: run the tests against all supported PHP versions [#55] from [@jrfnl].
+- GH Actions: report CS violations in the PR [#55] from [@jrfnl].
 
 [1.3.0]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/compare/v1.2.0...v1.3.0
+[#30]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/30
+[#34]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/34
+[#37]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/37
+[#41]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/41
+[#46]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/46
+[#48]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/48
+[#51]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/51
+[#52]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/52
+[#53]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/53
+[#54]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/54
+[#55]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/pull/55
 
 ## [1.2.0] - 2020-04-04
 
@@ -50,17 +81,31 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Fixed
 
-- Fixed vendor location for running from other folder from [@Erkens](https://github.com/Erkens).
+- Fixed vendor location for running from other folder from [@Erkens].
 
 ### Internal
 
-- Added a .gitattributes file from [@jrfnl](https://github.com/jrfnl), thanks for issue to [@ondrejmirtes](https://github.com/ondrejmirtes).
-- Fixed incorrect unit tests from [@jrfnl](https://github.com/jrfnl).
-- Fixed minor grammatical errors from [@jrfnl](https://github.com/jrfnl).
-- Added Travis: test against nightly (= PHP 8) from [@jrfnl](https://github.com/jrfnl).
-- Travis: removed sudo from [@jrfnl](https://github.com/jrfnl).
+- Added a .gitattributes file from [@jrfnl], thanks for issue to [@ondrejmirtes].
+- Fixed incorrect unit tests from [@jrfnl].
+- Fixed minor grammatical errors from [@jrfnl].
+- Added Travis: test against nightly (= PHP 8) from [@jrfnl].
+- Travis: removed sudo from [@jrfnl].
 - Added info about installing like not a dependency.
 - Cleaned readme - new organization from previous package.
-- Added checklist for new version from [@szepeviktor](https://github.com/szepeviktor).
+- Added checklist for new version from [@szepeviktor].
 
 [1.2.0]: https://github.com/php-parallel-lint/PHP-Parallel-Lint/compare/v1.1.0...v1.2.0
+
+[@Erkens]: https://github.com/Erkens
+[@OndraM]: https://github.com/OndraM
+[@arxeiss]: https://github.com/arxeiss
+[@glensc]: https://github.com/glensc
+[@jankonas]: https://github.com/jankonas
+[@jrfnl]: https://github.com/jrfnl
+[@mfn]: https://github.com/mfn
+[@ondrejmirtes]: https://github.com/ondrejmirtes
+[@reedy]: https://github.com/reedy
+[@roelofr]: https://github.com/roelofr
+[@szepeviktor]: https://github.com/szepeviktor
+[@lukas9393]: https://github.com/lukas9393
+
diff --git a/README.md b/README.md
index e5c762f..eb546e9 100644
--- a/README.md
+++ b/README.md
@@ -75,6 +75,7 @@ It is strongly recommended for existing users of the (unmaintained)
 - `--no-progress`   		Disable progress in console output.
 - `--checkstyle`    		Output results as Checkstyle XML.
 - `--json`          		Output results as JSON string (requires PHP 5.4).
+- `--gitlab`          		Output results for the GitLab Code Quality widget (requires PHP 5.4), see more in [Code Quality](https://docs.gitlab.com/ee/user/project/merge_requests/code_quality.html) documentation.
 - `--blame`         		Try to show git blame for row with error.
 - `--git <git>`     		Path to Git executable to show blame message (default: 'git').
 - `--stdin`         		Load files and folder to test from standard input.
diff --git a/composer.json b/composer.json
index ce7ed04..55d5812 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
     "require-dev": {
         "nette/tester": "^1.3 || ^2.0",
         "php-parallel-lint/php-console-highlighter": "~0.3",
-        "squizlabs/php_codesniffer": "^3.5"
+        "squizlabs/php_codesniffer": "^3.6"
     },
     "suggest": {
         "php-parallel-lint/php-console-highlighter": "Highlight syntax in code snippet"
diff --git a/src/Application.php b/src/Application.php
index d38e42d..4b4017e 100644
--- a/src/Application.php
+++ b/src/Application.php
@@ -4,7 +4,7 @@
 
 class Application
 {
-    const VERSION = '1.3.0';
+    const VERSION = '1.3.1';
 
     // Return codes
     const SUCCESS = 0,
@@ -87,6 +87,7 @@ private function showOptions()
     --no-colors             Disable colors in console output.
     --no-progress           Disable progress in console output.
     --json                  Output results as JSON string.
+    --gitlab                Output results for the GitLab Code Quality Widget.
     --checkstyle            Output results as Checkstyle XML.
     --blame                 Try to show git blame for row with error.
     --git <git>             Path to Git executable to show blame message (default: 'git').
diff --git a/src/Error.php b/src/Error.php
index 9041ab1..0c9f65f 100644
--- a/src/Error.php
+++ b/src/Error.php
@@ -1,6 +1,8 @@
 <?php
 namespace JakubOnderka\PhpParallelLint;
 
+use ReturnTypeWillChange;
+
 class Error implements \JsonSerializable
 {
     /** @var string */
@@ -57,6 +59,7 @@ public function getShortFilePath()
      * @return mixed data which can be serialized by <b>json_encode</b>,
      * which is a value of any type other than a resource.
      */
+    #[ReturnTypeWillChange]
     public function jsonSerialize()
     {
         return array(
@@ -87,6 +90,7 @@ class Blame implements \JsonSerializable
      * @return mixed data which can be serialized by <b>json_encode</b>,
      * which is a value of any type other than a resource.
      */
+    #[ReturnTypeWillChange]
     function jsonSerialize()
     {
         return array(
diff --git a/src/Manager.php b/src/Manager.php
index 63091b1..84b7434 100644
--- a/src/Manager.php
+++ b/src/Manager.php
@@ -4,6 +4,7 @@
 use JakubOnderka\PhpParallelLint\Contracts\SyntaxErrorCallback;
 use JakubOnderka\PhpParallelLint\Process\GitBlameProcess;
 use JakubOnderka\PhpParallelLint\Process\PhpExecutable;
+use ReturnTypeWillChange;
 
 class Manager
 {
@@ -82,6 +83,8 @@ protected function getDefaultOutput(Settings $settings)
         switch ($settings->format) {
             case Settings::FORMAT_JSON:
                 return new JsonOutput($writer);
+            case Settings::FORMAT_GITLAB:
+                return new GitLabOutput($writer);
             case Settings::FORMAT_CHECKSTYLE:
                 return new CheckstyleOutput($writer);
         }
@@ -224,6 +227,7 @@ public function __construct(\RecursiveDirectoryIterator $iterator, array $exclud
      * @link http://php.net/manual/en/filteriterator.accept.php
      * @return bool true if the current element is acceptable, otherwise false.
      */
+    #[ReturnTypeWillChange]
     public function accept()
     {
         $current = $this->current()->getPathname();
@@ -243,6 +247,7 @@ public function accept()
      * @link http://php.net/manual/en/recursivefilteriterator.haschildren.php
      * @return bool true if the inner iterator has children, otherwise false
      */
+    #[ReturnTypeWillChange]
     public function hasChildren()
     {
         return $this->iterator->hasChildren();
@@ -255,6 +260,7 @@ public function hasChildren()
      * @link http://php.net/manual/en/recursivefilteriterator.getchildren.php
      * @return \RecursiveFilterIterator containing the inner iterator's children.
      */
+    #[ReturnTypeWillChange]
     public function getChildren()
     {
         return new self($this->iterator->getChildren(), $this->excluded);
diff --git a/src/Output.php b/src/Output.php
index c51d11b..974dde8 100644
--- a/src/Output.php
+++ b/src/Output.php
@@ -85,6 +85,81 @@ public function writeResult(Result $result, ErrorFormatter $errorFormatter, $ign
     }
 }
 
+class GitLabOutput implements Output
+{
+    /** @var IWriter */
+    protected $writer;
+
+    /**
+     * @param IWriter $writer
+     */
+    public function __construct(IWriter $writer)
+    {
+        $this->writer = $writer;
+    }
+
+    public function ok()
+    {
+
+    }
+
+    public function skip()
+    {
+
+    }
+
+    public function error()
+    {
+
+    }
+
+    public function fail()
+    {
+
+    }
+
+    public function setTotalFileCount($count)
+    {
+
+    }
+
+    public function writeHeader($phpVersion, $parallelJobs, $hhvmVersion = null)
+    {
+
+    }
+
+    public function writeResult(Result $result, ErrorFormatter $errorFormatter, $ignoreFails)
+    {
+        $errors = array();
+        foreach ($result->getErrors() as $error) {
+            $message = $error->getMessage();
+            $line = 1;
+            if ($error instanceof SyntaxError) {
+                $line = $error->getLine();
+            }
+            $filePath = $error->getFilePath();
+            $result = array(
+                'type' => 'issue',
+                'check_name' => 'Parse error',
+                'description' => $message,
+                'categories' => 'Style',
+                'fingerprint' => md5($filePath . $message . $line),
+                'severity' => 'minor',
+                'location' => array(
+                    'path' => $filePath,
+                    'lines' => array(
+                        'begin' => $line,
+                    ),
+                ),
+            );
+            array_push($errors, $result);
+        }
+
+        $string = json_encode($errors) . PHP_EOL;
+        $this->writer->write($string);
+    }
+}
+
 class TextOutput implements Output
 {
     const TYPE_DEFAULT = 'default',
diff --git a/src/Result.php b/src/Result.php
index 6004374..9f6a368 100644
--- a/src/Result.php
+++ b/src/Result.php
@@ -1,6 +1,8 @@
 <?php
 namespace JakubOnderka\PhpParallelLint;
 
+use ReturnTypeWillChange;
+
 class Result implements \JsonSerializable
 {
     /** @var Error[] */
@@ -154,6 +156,7 @@ public function getTestTime()
      * @return mixed data which can be serialized by <b>json_encode</b>,
      * which is a value of any type other than a resource.
      */
+    #[ReturnTypeWillChange]
     function jsonSerialize()
     {
         return array(
diff --git a/src/Settings.php b/src/Settings.php
index 3e03a71..40cb8b1 100644
--- a/src/Settings.php
+++ b/src/Settings.php
@@ -13,6 +13,7 @@ class Settings
 
     const FORMAT_TEXT = 'text';
     const FORMAT_JSON = 'json';
+    const FORMAT_GITLAB = 'gitlab';
     const FORMAT_CHECKSTYLE = 'checkstyle';
 
     /**
@@ -179,6 +180,10 @@ public static function parseArguments(array $arguments)
                         $settings->format = self::FORMAT_JSON;
                         break;
 
+                    case '--gitlab':
+                        $settings->format = self::FORMAT_GITLAB;
+                        break;
+
                     case '--checkstyle':
                         $settings->format = self::FORMAT_CHECKSTYLE;
                         break;
diff --git a/src/exceptions.php b/src/exceptions.php
index 3893b83..b96f28a 100644
--- a/src/exceptions.php
+++ b/src/exceptions.php
@@ -1,8 +1,11 @@
 <?php
 namespace JakubOnderka\PhpParallelLint;
 
+use ReturnTypeWillChange;
+
 class Exception extends \Exception implements \JsonSerializable
 {
+    #[ReturnTypeWillChange]
     public function jsonSerialize()
     {
         return array(
diff --git a/tests/Output.phpt b/tests/Output.phpt
new file mode 100644
index 0000000..95814a5
--- /dev/null
+++ b/tests/Output.phpt
@@ -0,0 +1,95 @@
+<?php
+
+/**
+ * @testCase
+ */
+
+require __DIR__ . '/../vendor/autoload.php';
+
+use JakubOnderka\PhpParallelLint\ErrorFormatter;
+use JakubOnderka\PhpParallelLint\GitLabOutput;
+use JakubOnderka\PhpParallelLint\IWriter;
+use JakubOnderka\PhpParallelLint\Result;
+use JakubOnderka\PhpParallelLint\SyntaxError;
+use Tester\Assert;
+
+class OutputTest extends Tester\TestCase
+{
+    /**
+     * @dataProvider getGitLabOutputData
+     */
+    public function testGitLabOutput($errors)
+    {
+        $result = new Result($errors, array(), array(), 0);
+        $writer = new TestWriter();
+        $output = new GitLabOutput($writer);
+
+        $output->writeResult($result, new ErrorFormatter(), true);
+
+        $result = (array) json_decode($writer->getLogs());
+
+        for ($i = 0; $i < count($result) && $i < count($errors); $i++) {
+            $message = $errors[$i]->getMessage();
+            $filePath = $errors[$i]->getFilePath();
+            $line = 1;
+            if ($errors[$i] instanceof SyntaxError) {
+                $line = $errors[$i]->getLine();
+            }
+            Assert::equal($result[$i]->type, 'issue');
+            Assert::equal($result[$i]->check_name, 'Parse error');
+            Assert::equal($result[$i]->categories, 'Style');
+            Assert::equal($result[$i]->severity, 'minor');
+            Assert::equal($result[$i]->description, $message);
+            Assert::equal($result[$i]->fingerprint, md5($filePath . $message . $line));
+            Assert::equal($result[$i]->location->path, $filePath);
+            Assert::equal($result[$i]->location->lines->begin, $line);
+        }
+    }
+
+    public function getGitLabOutputData()
+    {
+        return array(
+            array(
+                'errors' => array()
+            ),
+            array(
+                'errors' => array(
+                    new SyntaxError('foo/bar.php', "Parse error: syntax error, unexpected in foo/bar.php on line 52")
+                )
+            ),
+            array(
+                'errors' => array(
+                    new JakubOnderka\PhpParallelLint\Error('foo/bar.php', "PHP Parse error: syntax error, unexpected ';'")
+                )
+            ),
+            array(
+                'errors' => array(
+                    new SyntaxError('foo/bar.php', "Parse error: syntax error, unexpected in foo/bar.php on line 52"),
+                    new JakubOnderka\PhpParallelLint\Error('foo/bar.php', "PHP Parse error: syntax error, unexpected ';'")
+                )
+            ),
+        );
+    }
+}
+
+class TestWriter implements IWriter
+{
+    /** @var string */
+    protected $logs = "";
+
+    /**
+     * @param string $string
+     */
+    public function write($string)
+    {
+        $this->logs .= $string;
+    }
+
+    public function getLogs()
+    {
+        return $this->logs;
+    }
+}
+
+$testCase = new OutputTest;
+$testCase->run();
diff --git a/tests/Settings.parseArguments.phpt b/tests/Settings.parseArguments.phpt
index 0a83673..a669195 100644
--- a/tests/Settings.parseArguments.phpt
+++ b/tests/Settings.parseArguments.phpt
@@ -103,6 +103,14 @@ class SettingsParseArgumentsTest extends Tester\TestCase
         Assert::equal(Settings::FORMAT_JSON, $settings->format);
     }
 
+    public function testGitLabOutput()
+    {
+        $commandLine = './parallel-lint --gitlab .';
+        $argv = explode(" ", $commandLine);
+        $settings = Settings::parseArguments($argv);
+        Assert::equal(Settings::FORMAT_GITLAB, $settings->format);
+    }
+
     public function testCheckstyleOutput()
     {
         $commandLine = './parallel-lint --checkstyle .';