diff --git a/src/Core/Scope.php b/src/Core/Scope.php
index a1c0c2b86..9eb244f9a 100644
--- a/src/Core/Scope.php
+++ b/src/Core/Scope.php
@@ -58,7 +58,7 @@ public function __construct(callable $callback, $args = [])
     /**
      * Close and clean up the scope. Runs the initial callback provided.
      */
-    public function close()
+    public function close(): void
     {
         call_user_func_array($this->callback, $this->args);
     }
diff --git a/src/Trace/RequestHandler.php b/src/Trace/RequestHandler.php
index 1a969949a..19ff3dd77 100644
--- a/src/Trace/RequestHandler.php
+++ b/src/Trace/RequestHandler.php
@@ -17,12 +17,10 @@
 
 namespace OpenCensus\Trace;
 
-use OpenCensus\Core\Context;
 use OpenCensus\Core\Scope;
 use OpenCensus\Trace\Exporter\ExporterInterface;
 use OpenCensus\Trace\Propagator\ArrayHeaders;
 use OpenCensus\Trace\Sampler\SamplerInterface;
-use OpenCensus\Trace\Span;
 use OpenCensus\Trace\Tracer\ContextTracer;
 use OpenCensus\Trace\Tracer\ExtensionTracer;
 use OpenCensus\Trace\Tracer\NullTracer;
@@ -36,8 +34,8 @@
  */
 class RequestHandler
 {
-    const DEFAULT_ROOT_SPAN_NAME = 'main';
-    const ATTRIBUTE_MAP = [
+    private const DEFAULT_ROOT_SPAN_NAME = 'main';
+    private const ATTRIBUTE_MAP = [
         Span::ATTRIBUTE_HOST => ['HTTP_HOST', 'SERVER_NAME'],
         Span::ATTRIBUTE_PORT => ['SERVER_PORT'],
         Span::ATTRIBUTE_METHOD => ['REQUEST_METHOD'],
@@ -131,7 +129,7 @@ public function __construct(
      * reports using the provided ExporterInterface. Adds additional attributes to
      * the root span detected from the response.
      */
-    public function onExit()
+    public function onExit(): void
     {
         $this->addCommonRequestAttributes($this->headers->toArray());
 
@@ -145,7 +143,7 @@ public function onExit()
      *
      * @return TracerInterface
      */
-    public function tracer()
+    public function tracer(): TracerInterface
     {
         return $this->tracer;
     }
@@ -159,6 +157,7 @@ public function tracer()
      * @param array $spanOptions Options for the span. See
      *        <a href="Span.html#method___construct">OpenCensus\Trace\Span::__construct()</a>
      * @param callable $callable The callable to instrument.
+     * @param array $arguments
      * @return mixed Returns whatever the callable returns
      */
     public function inSpan(array $spanOptions, callable $callable, array $arguments = [])
@@ -174,7 +173,7 @@ public function inSpan(array $spanOptions, callable $callable, array $arguments
      *        <a href="Span.html#method___construct">OpenCensus\Trace\Span::__construct()</a>
      * @return Span
      */
-    public function startSpan(array $spanOptions = [])
+    public function startSpan(array $spanOptions = []): Span
     {
         return $this->tracer->startSpan($spanOptions);
     }
@@ -186,7 +185,7 @@ public function startSpan(array $spanOptions = [])
      * @param Span $span
      * @return Scope
      */
-    public function withSpan(Span $span)
+    public function withSpan(Span $span): Scope
     {
         return $this->tracer->withSpan($span);
     }
@@ -200,7 +199,7 @@ public function withSpan(Span $span)
      *
      *      @type Span $span The span to add the attribute to.
      */
-    public function addAttribute($attribute, $value, $options = [])
+    public function addAttribute($attribute, $value, $options = []): void
     {
         $this->tracer->addAttribute($attribute, $value, $options);
     }
@@ -215,7 +214,7 @@ public function addAttribute($attribute, $value, $options = [])
      *      @type array $attributes Attributes for this annotation.
      *      @type \DateTimeInterface|int|float $time The time of this event.
      */
-    public function addAnnotation($description, $options = [])
+    public function addAnnotation($description, $options = []): void
     {
         $this->tracer->addAnnotation($description, $options);
     }
@@ -233,7 +232,7 @@ public function addAnnotation($description, $options = [])
      *      @type array $attributes Attributes for this annotation.
      *      @type \DateTimeInterface|int|float $time The time of this event.
      */
-    public function addLink($traceId, $spanId, $options = [])
+    public function addLink($traceId, $spanId, $options = []): void
     {
         $this->tracer->addLink($traceId, $spanId, $options);
     }
@@ -253,12 +252,12 @@ public function addLink($traceId, $spanId, $options = [])
      *            uncompressed.
      *      @type \DateTimeInterface|int|float $time The time of this event.
      */
-    public function addMessageEvent($type, $id, $options)
+    public function addMessageEvent($type, $id, $options): void
     {
         $this->tracer->addMessageEvent($type, $id, $options);
     }
 
-    public function addCommonRequestAttributes(array $headers)
+    private function addCommonRequestAttributes(array $headers): void
     {
         if ($responseCode = http_response_code()) {
             $this->rootSpan->setStatus($responseCode, "HTTP status code: $responseCode");
@@ -275,7 +274,7 @@ public function addCommonRequestAttributes(array $headers)
         }
     }
 
-    private function startTimeFromHeaders(array $headers)
+    private function startTimeFromHeaders(array $headers): ?string
     {
         if (array_key_exists('REQUEST_TIME_FLOAT', $headers)) {
             return $headers['REQUEST_TIME_FLOAT'];
@@ -286,15 +285,12 @@ private function startTimeFromHeaders(array $headers)
         return null;
     }
 
-    private function nameFromHeaders(array $headers)
+    private function nameFromHeaders(array $headers): string
     {
-        if (array_key_exists('REQUEST_URI', $headers)) {
-            return $headers['REQUEST_URI'];
-        }
-        return self::DEFAULT_ROOT_SPAN_NAME;
+        return $headers['REQUEST_URI'] ?? self::DEFAULT_ROOT_SPAN_NAME;
     }
 
-    private function detectKey(array $keys, array $array)
+    private function detectKey(array $keys, array $array): ?string
     {
         foreach ($keys as $key) {
             if (array_key_exists($key, $array)) {
diff --git a/src/Trace/Tracer.php b/src/Trace/Tracer.php
index 2361b2bb4..0e1d1b5cb 100644
--- a/src/Trace/Tracer.php
+++ b/src/Trace/Tracer.php
@@ -18,7 +18,6 @@
 namespace OpenCensus\Trace;
 
 use OpenCensus\Core\Scope;
-use OpenCensus\Trace\Span;
 use OpenCensus\Trace\Sampler\AlwaysSampleSampler;
 use OpenCensus\Trace\Sampler\SamplerInterface;
 use OpenCensus\Trace\Exporter\ExporterInterface;
@@ -117,7 +116,7 @@ class Tracer
      *      @type array $headers Optional array of headers to use in place of $_SERVER
      * @return RequestHandler
      */
-    public static function start(ExporterInterface $reporter, array $options = [])
+    public static function start(ExporterInterface $reporter, array $options = []): RequestHandler
     {
         $sampler = array_key_exists('sampler', $options)
             ? $options['sampler']
@@ -187,12 +186,9 @@ public static function inSpan(array $spanOptions, callable $callable, array $arg
      *      <a href="Span.html#method___construct">OpenCensus\Trace\Span::__construct()</a>
      * @return Span
      */
-    public static function startSpan(array $spanOptions = [])
+    public static function startSpan(array $spanOptions = []): Span
     {
-        if (!isset(self::$instance)) {
-            return new Span();
-        }
-        return self::$instance->startSpan($spanOptions);
+        return isset(self::$instance) ? self::$instance->startSpan($spanOptions) : new Span();
     }
 
     /**
@@ -213,13 +209,12 @@ public static function startSpan(array $spanOptions = [])
      * @param Span $span
      * @return Scope
      */
-    public static function withSpan(Span $span)
+    public static function withSpan(Span $span): Scope
     {
-        if (!isset(self::$instance)) {
-            return new Scope(function () {
-            });
-        }
-        return self::$instance->withSpan($span);
+        return isset(self::$instance) ? self::$instance->withSpan($span) : new Scope(
+            function () {
+            }
+        );
     }
 
     /**
@@ -231,12 +226,11 @@ public static function withSpan(Span $span)
      *
      *      @type Span $span The span to add the attribute to.
      */
-    public static function addAttribute($attribute, $value, $options = [])
+    public static function addAttribute($attribute, $value, $options = []): void
     {
-        if (!isset(self::$instance)) {
-            return;
+        if (isset(self::$instance)) {
+            self::$instance->addAttribute($attribute, $value, $options);
         }
-        return self::$instance->addAttribute($attribute, $value, $options);
     }
 
     /**
@@ -249,12 +243,11 @@ public static function addAttribute($attribute, $value, $options = [])
      *      @type array $attributes Attributes for this annotation.
      *      @type \DateTimeInterface|int|float $time The time of this event.
      */
-    public static function addAnnotation($description, $options = [])
+    public static function addAnnotation($description, $options = []): void
     {
-        if (!isset(self::$instance)) {
-            return;
+        if (isset(self::$instance)) {
+            self::$instance->addAnnotation($description, $options);
         }
-        return self::$instance->addAnnotation($description, $options);
     }
 
     /**
@@ -270,12 +263,11 @@ public static function addAnnotation($description, $options = [])
      *      @type array $attributes Attributes for this annotation.
      *      @type \DateTimeInterface|int|float $time The time of this event.
      */
-    public static function addLink($traceId, $spanId, $options = [])
+    public static function addLink($traceId, $spanId, $options = []): void
     {
-        if (!isset(self::$instance)) {
-            return;
+        if (isset(self::$instance)) {
+            self::$instance->addLink($traceId, $spanId, $options);
         }
-        return self::$instance->addLink($traceId, $spanId, $options);
     }
 
     /**
@@ -293,12 +285,11 @@ public static function addLink($traceId, $spanId, $options = [])
      *            uncompressed.
      *      @type \DateTimeInterface|int|float $time The time of this event.
      */
-    public static function addMessageEvent($type, $id, $options = [])
+    public static function addMessageEvent($type, $id, $options = []): void
     {
-        if (!isset(self::$instance)) {
-            return;
+        if (isset(self::$instance)) {
+            self::$instance->addMessageEvent($type, $id, $options);
         }
-        return self::$instance->addMessageEvent($type, $id, $options);
     }
 
     /**
@@ -306,11 +297,8 @@ public static function addMessageEvent($type, $id, $options = [])
      *
      * @return SpanContext
      */
-    public static function spanContext()
+    public static function spanContext(): SpanContext
     {
-        if (!isset(self::$instance)) {
-            return new SpanContext(null, null, false);
-        }
-        return self::$instance->tracer()->spanContext();
+        return isset(self::$instance) ? self::$instance->tracer()->spanContext() : new SpanContext(null, null, false);
     }
 }