Fix array to string conversion warning in Request::getSize()

Headers can now be arrays (after recent changes allowing array headers).
The getSize() method was attempting to directly implode headers, causing
a warning when a header value was an array.

This fix properly handles both string and array header values by joining
array values with commas (standard HTTP header format) before calculating
the request size.

Added test case to verify the fix works correctly with array headers.

Author: ChiragAgg5k

src/Http/Request.php

@@ -332,7 +332,16 @@ abstract public function removeHeader(string $key): static;
      */
     public function getSize(): int
     {
-        return \mb_strlen(\implode("\n", $this->generateHeaders()), '8bit') + \mb_strlen(\file_get_contents('php://input'), '8bit');
+        $headers = $this->generateHeaders();
+        $headerStrings = [];
+        foreach ($headers as $key => $value) {
+            if (\is_array($value)) {
+                $headerStrings[] = $key . ': ' . \implode(', ', $value);
+            } else {
+                $headerStrings[] = $key . ': ' . $value;
+            }
+        }
+        return \mb_strlen(\implode("\n", $headerStrings), '8bit') + \mb_strlen(\file_get_contents('php://input'), '8bit');
     }
 
     /**

tests/RequestTest.php

@@ -313,4 +313,23 @@ public function testCanGetRange()
         $this->assertEquals(null, $this->request->getRangeStart());
         $this->assertEquals(null, $this->request->getRangeEnd());
     }
+
+    public function testCanGetSizeWithArrayHeaders()
+    {
+        $this->request->addHeader('content-type', 'application/json');
+
+        $reflection = new \ReflectionClass($this->request);
+        $headersProperty = $reflection->getProperty('headers');
+        $headersProperty->setAccessible(true);
+
+        $headers = $headersProperty->getValue($this->request) ?? [];
+        $headers['accept'] = ['application/json', 'text/html'];
+        $headers['x-custom'] = ['value1', 'value2', 'value3'];
+        $headersProperty->setValue($this->request, $headers);
+
+        $size = $this->request->getSize();
+
+        $this->assertIsInt($size);
+        $this->assertGreaterThan(0, $size);
+    }
 }