diff --git a/composer.json b/composer.json
index 33a0c646..458ec4c4 100644
--- a/composer.json
+++ b/composer.json
@@ -17,6 +17,9 @@
         "forum": "https://discourse.laminas.dev"
     },
     "config": {
+        "allow-plugins": {
+            "dealerdirect/phpcodesniffer-composer-installer": true
+        },
         "sort-packages": true
     },
     "extra": {
diff --git a/src/Formatter/Simple.php b/src/Formatter/Simple.php
index 5a360d81..5c4c2d13 100644
--- a/src/Formatter/Simple.php
+++ b/src/Formatter/Simple.php
@@ -7,6 +7,7 @@
 use Laminas\Log\Exception;
 use Traversable;
 
+use function array_key_exists;
 use function count;
 use function is_array;
 use function is_string;
@@ -65,7 +66,7 @@ public function format($event)
 
         $event = parent::format($event);
         foreach ($event as $name => $value) {
-            if ('extra' === $name && count($value)) {
+            if ('extra' === $name && is_array($value) && count($value)) {
                 $value = $this->normalize($value);
             } elseif ('extra' === $name) {
                 // Don't print an empty array
@@ -75,7 +76,7 @@ public function format($event)
         }
 
         if (
-            isset($event['extra']) && empty($event['extra'])
+            array_key_exists('extra', $event) && empty($event['extra'])
             && false !== strpos($this->format, '%extra%')
         ) {
             $output = rtrim($output, ' ');
diff --git a/test/Formatter/SimpleTest.php b/test/Formatter/SimpleTest.php
index d344bdf8..4e3f367e 100644
--- a/test/Formatter/SimpleTest.php
+++ b/test/Formatter/SimpleTest.php
@@ -4,11 +4,18 @@
 
 namespace LaminasTest\Log\Formatter;
 
+use ArrayIterator;
 use DateTime;
+use EmptyIterator;
 use Laminas\Log\Exception\InvalidArgumentException;
 use Laminas\Log\Formatter\Simple;
+use LaminasTest\Log\TestAsset\StringObject;
 use PHPUnit\Framework\TestCase;
 use RuntimeException;
+use stdClass;
+
+use function fopen;
+use function range;
 
 class SimpleTest extends TestCase
 {
@@ -53,6 +60,82 @@ public function testDefaultFormat(): void
         $this->assertEquals($outputExpected, $formatter->format($fields));
     }
 
+    public function testFormatAllTypes(): void
+    {
+        $date        = new DateTime('2012-08-28T18:15:00Z');
+        $object      = new stdClass();
+        $object->foo = 'bar';
+        $fields      = [
+            'timestamp'    => $date,
+            'message'      => 'foo',
+            'priority'     => 42,
+            'priorityName' => 'bar',
+            'extra'        => [
+                'float'             => 0.2,
+                'boolean'           => false,
+                'array_empty'       => [],
+                'array'             => range(0, 4),
+                'traversable_empty' => new EmptyIterator(),
+                'traversable'       => new ArrayIterator(['id', 42]),
+                'null'              => null,
+                'object_empty'      => new stdClass(),
+                'object'            => $object,
+                'string object'     => new StringObject(),
+                'resource'          => fopen('php://stdout', 'w'),
+            ],
+        ];
+
+        $outputExpected = '2012-08-28T18:15:00+00:00 bar (42): foo {'
+            . '"float":0.2,'
+            . '"boolean":false,'
+            . '"array_empty":"[]",'
+            . '"array":"[0,1,2,3,4]",'
+            . '"traversable_empty":"[]",'
+            . '"traversable":"[\"id\",42]",'
+            . '"null":null,'
+            . '"object_empty":"object(stdClass) {}",'
+            . '"object":"object(stdClass) {\"foo\":\"bar\"}",'
+            . '"string object":"Hello World",'
+            . '"resource":"resource(stream)"}';
+        $formatter      = new Simple();
+
+        $this->assertEquals($outputExpected, $formatter->format($fields));
+    }
+
+    public function testFormatExtraArrayKeyWithNonArrayValue(): void
+    {
+        $date   = new DateTime('2012-08-28T18:15:00Z');
+        $fields = [
+            'timestamp'    => $date,
+            'message'      => 'foo',
+            'priority'     => 42,
+            'priorityName' => 'bar',
+            'extra'        => '',
+        ];
+
+        $outputExpected = '2012-08-28T18:15:00+00:00 bar (42): foo';
+        $formatter      = new Simple();
+
+        $this->assertEquals($outputExpected, $formatter->format($fields));
+    }
+
+    public function testFormatExtraArrayKeyWithNullValue(): void
+    {
+        $date   = new DateTime('2012-08-28T18:15:00Z');
+        $fields = [
+            'timestamp'    => $date,
+            'message'      => 'foo',
+            'priority'     => 42,
+            'priorityName' => 'bar',
+            'extra'        => null,
+        ];
+
+        $outputExpected = '2012-08-28T18:15:00+00:00 bar (42): foo';
+        $formatter      = new Simple();
+
+        $this->assertEquals($outputExpected, $formatter->format($fields));
+    }
+
     /**
      * @dataProvider provideDateTimeFormats
      */