diff --git a/omnitools/src/DataTypes/Result/Err.php b/omnitools/src/DataTypes/Result/Err.php
new file mode 100644
--- /dev/null
+++ b/omnitools/src/DataTypes/Result/Err.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace Keruald\OmniTools\DataTypes\Result;
+
+use Exception;
+use InvalidArgumentException;
+use Throwable;
+
+class Err extends Result {
+    private ?Throwable $error;
+
+    public function __construct (Throwable $error = null) {
+        $this->error = $error;
+    }
+
+    public function isOK () : false {
+        return false;
+    }
+
+    public function isError () : true {
+        return true;
+    }
+
+    public function getValue () : mixed {
+        throw new InvalidArgumentException(<<<'EOD'
+This result is an error, so it doesn't have a value.
+You can check first with isOK() if this is a value.
+Or if you want the error, use getError().
+EOD
+);
+    }
+
+    public function getError () : Throwable {
+        return $this->error;
+    }
+
+    public function setError (Throwable $error) : void {
+        $this->error = $error;
+    }
+
+    public function map (callable $callable) : self {
+        return $this;
+    }
+
+    public function mapErr (callable $callable) : self {
+        $error = $callable($this->error);
+
+        return new self($error);
+    }
+
+    public function orElse (mixed $default) : mixed {
+        return $default;
+    }
+}
diff --git a/omnitools/src/DataTypes/Result/Ok.php b/omnitools/src/DataTypes/Result/Ok.php
new file mode 100644
--- /dev/null
+++ b/omnitools/src/DataTypes/Result/Ok.php
@@ -0,0 +1,72 @@
+<?php
+
+namespace Keruald\OmniTools\DataTypes\Result;
+
+use InvalidArgumentException;
+
+class Ok extends Result {
+    private mixed $value = null;
+
+    private string $type = "NULL";
+
+    public function __construct ($value = null) {
+        if ($value !== null) {
+            $this->setValue($value);
+        }
+    }
+
+    public function isOK () : true {
+        return true;
+    }
+
+    public function isError () : false {
+        return false;
+    }
+
+    public function getValue () : mixed {
+        return $this->value;
+    }
+
+    public function setValue (mixed $value) : void {
+        $type = self::getTypeOf($value);
+        if (!$this->isAcceptableValueType($type)) {
+            throw new InvalidArgumentException(<<<'EOD'
+When you mutate the value of an Ok object, you can't mutate the object type.
+Please consider return a new Ok instead.
+EOD
+            );
+        }
+
+        $this->value = $value;
+        $this->type = $type;
+    }
+
+    private function isAcceptableValueType (string $type) : bool {
+        return $this->value === null || $type === $this->type;
+    }
+
+
+    private static function getTypeOf ($v) : string {
+        $type = gettype($v);
+
+        if ($type === "object") {
+            return get_class($v);
+        }
+
+        return $type;
+    }
+
+    public function map (callable $callable) : self {
+        $value = $callable($this->value);
+
+        return new self($value);
+    }
+
+    public function mapErr (callable $callable) : self {
+        return $this;
+    }
+
+    public function orElse (mixed $default) : mixed {
+        return $this->value;
+    }
+}
diff --git a/omnitools/src/DataTypes/Result/Result.php b/omnitools/src/DataTypes/Result/Result.php
new file mode 100644
--- /dev/null
+++ b/omnitools/src/DataTypes/Result/Result.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Keruald\OmniTools\DataTypes\Result;
+
+abstract class Result {
+    public abstract function isOK () : bool;
+    public abstract function isError () : bool;
+
+    public abstract function getValue () : mixed;
+
+    public abstract function map(callable $callable) : self;
+    public abstract function mapErr(callable $callable): self;
+
+    public abstract function orElse(mixed $default) : mixed;
+}
diff --git a/omnitools/tests/DataTypes/Result/ErrTest.php b/omnitools/tests/DataTypes/Result/ErrTest.php
new file mode 100644
--- /dev/null
+++ b/omnitools/tests/DataTypes/Result/ErrTest.php
@@ -0,0 +1,56 @@
+<?php
+declare(strict_types=1);
+
+namespace Keruald\OmniTools\Tests\DataTypes\Result;
+
+use DivisionByZeroError;
+use Exception;
+use Throwable;
+
+use Keruald\OmniTools\DataTypes\Result\Err;
+use PHPUnit\Framework\TestCase;
+
+class ErrTest extends TestCase {
+    public function setUp () : void {
+        $this->v = new Err;
+        $this->v->setError(new DivisionByZeroError());
+    }
+
+    public function testIsOk () : void {
+        $this->AssertFalse($this->v->isOk());
+    }
+
+    public function testIsError () : void {
+        $this->assertTrue($this->v->isError());
+    }
+
+    public function testGetValue () : void {
+        $this->expectException("InvalidArgumentException");
+        $this->v->getValue();
+    }
+
+    public function testMap () : void {
+        $callback = function ($n) {
+            return $n * 2;
+        };
+
+        $mapped_v = $this->v->map($callback);
+
+        $this->assertEquals($mapped_v, $this->v);
+    }
+
+    public function testMapErr () : void {
+        $callback = function (Throwable $ex) {
+            return new Exception();
+        };
+
+        $mapped_v = $this->v->mapErr($callback);
+        $this->assertInstanceOf(Exception::class, $mapped_v->getError());
+    }
+
+    public function testOrElse () : void {
+        $value = $this->v->orElse(666);
+
+        $this->assertEquals(666, $value);
+    }
+}
diff --git a/omnitools/tests/DataTypes/Result/OkTest.php b/omnitools/tests/DataTypes/Result/OkTest.php
new file mode 100644
--- /dev/null
+++ b/omnitools/tests/DataTypes/Result/OkTest.php
@@ -0,0 +1,65 @@
+<?php
+declare(strict_types=1);
+
+namespace Keruald\OmniTools\Tests\DataTypes\Result;
+
+use Exception;
+
+use Keruald\OmniTools\DataTypes\Result\Ok;
+use PHPUnit\Framework\TestCase;
+
+class OkTest extends TestCase {
+
+    public function setUp () : void {
+        $this->v = new Ok;
+        $this->v->setValue(42);
+    }
+
+    public function testIsOk () : void {
+        $this->AssertTrue($this->v->isOk());
+    }
+
+    public function testIsError () : void {
+        $this->assertFalse($this->v->isError());
+    }
+
+    public function testGetValue () : void {
+        $this->assertEquals(42, $this->v->getValue());
+    }
+
+    public function testSetValue () : void {
+        $this->v->setValue(666);
+        $this->assertEquals(666, $this->v->getValue());
+    }
+
+    public function testSetValueWhenTypeIsMutated () : void {
+        $this->expectException("InvalidArgumentException");
+        $this->v->setValue("Another type");
+    }
+
+    public function testMap () : void {
+        $callback = function ($n) {
+            return $n * 2;
+        };
+
+        $mapped_v = $this->v->map($callback);
+
+        $this->assertEquals(84, $mapped_v->getValue());
+    }
+
+    public function testMapErr () : void {
+        $callback = function (Exception $ex) {
+            return new Exception();
+        };
+
+        $mapped_v = $this->v->mapErr($callback);
+
+        $this->assertEquals($mapped_v, $this->v);
+    }
+
+    public function testOrElse () : void {
+        $value = $this->v->orElse(666);
+
+        $this->assertEquals(42, $value);
+    }
+}
diff --git a/phpunit.xml b/phpunit.xml
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -20,6 +20,10 @@
 
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.3/phpunit.xsd"
+         displayDetailsOnTestsThatTriggerDeprecations="true"
+         displayDetailsOnTestsThatTriggerErrors="true"
+         displayDetailsOnTestsThatTriggerWarnings="true"
+         displayDetailsOnTestsThatTriggerNotices="true"
          bootstrap="vendor/autoload.php"
          cacheDirectory=".phpunit.cache"
          stopOnFailure="false">