diff --git a/export.php b/export.php
index a16beb0..ed6eb84 100644
--- a/export.php
+++ b/export.php
@@ -22,19 +22,31 @@
 
 foreach ($src as $class) {
     $class = "Jaybizzle\\CrawlerDetect\\Fixtures\\$class";
-    $object = new $class;
+    $object = new $class();
 
     outputJson($object);
     outputTxt($object);
 }
 
-function outputJson($object)
+/**
+ * Output data to JSON file.
+ *
+ * @param object $object Instance of AbstractProvider
+ * @return void
+ */
+function outputJson(object $object): void
 {
     $className = (new ReflectionClass($object))->getShortName();
     file_put_contents("raw/$className.json", json_encode($object->getAll()));
 }
 
-function outputTxt($object)
+/**
+ * Output data to text file.
+ *
+ * @param object $object Instance of AbstractProvider
+ * @return void
+ */
+function outputTxt(object $object): void
 {
     $className = (new ReflectionClass($object))->getShortName();
     file_put_contents("raw/$className.txt", implode(PHP_EOL, $object->getAll()));
diff --git a/src/CrawlerDetect.php b/src/CrawlerDetect.php
index 497864f..ed583f5 100644
--- a/src/CrawlerDetect.php
+++ b/src/CrawlerDetect.php
@@ -22,7 +22,7 @@ class CrawlerDetect
      *
      * @var string|null
      */
-    protected $userAgent;
+    protected $userAgent = null;
 
     /**
      * Headers that contain a user agent.
@@ -75,8 +75,11 @@ class CrawlerDetect
 
     /**
      * Class constructor.
+     *
+     * @param array<string, string>|null $headers HTTP headers array
+     * @param string|null $userAgent User agent string
      */
-    public function __construct(?array $headers = null, $userAgent = null)
+    public function __construct(?array $headers = null, ?string $userAgent = null)
     {
         $this->crawlers = new Crawlers;
         $this->exclusions = new Exclusions;
@@ -92,10 +95,10 @@ public function __construct(?array $headers = null, $userAgent = null)
     /**
      * Compile the regex patterns into one regex string.
      *
-     * @param array
-     * @return string
+     * @param array<int, string> $patterns Array of regex patterns
+     * @return string Compiled regex pattern
      */
-    public function compileRegex($patterns)
+    public function compileRegex(array $patterns): string
     {
         return '('.implode('|', $patterns).')';
     }
@@ -103,9 +106,10 @@ public function compileRegex($patterns)
     /**
      * Set HTTP headers.
      *
-     * @param  array|null  $httpHeaders
+     * @param array<string, string>|null $httpHeaders HTTP headers array
+     * @return void
      */
-    public function setHttpHeaders($httpHeaders)
+    public function setHttpHeaders(?array $httpHeaders): void
     {
         // Use global _SERVER if $httpHeaders aren't defined.
         if (! is_array($httpHeaders) || ! count($httpHeaders)) {
@@ -127,9 +131,9 @@ public function setHttpHeaders($httpHeaders)
     /**
      * Return user agent headers.
      *
-     * @return array
+     * @return array<int, string> Array of user agent header keys
      */
-    public function getUaHttpHeaders()
+    public function getUaHttpHeaders(): array
     {
         return $this->uaHttpHeaders->getAll();
     }
@@ -137,16 +141,19 @@ public function getUaHttpHeaders()
     /**
      * Set the user agent.
      *
-     * @param  string|null  $userAgent
+     * @param string|null $userAgent User agent string
+     * @return string|null The set user agent
      */
-    public function setUserAgent($userAgent)
+    public function setUserAgent(?string $userAgent): ?string
     {
         if (is_null($userAgent)) {
+            $userAgent = '';
             foreach ($this->getUaHttpHeaders() as $altHeader) {
                 if (isset($this->httpHeaders[$altHeader])) {
                     $userAgent .= $this->httpHeaders[$altHeader].' ';
                 }
             }
+            $userAgent = $userAgent !== '' ? $userAgent : null;
         }
 
         return $this->userAgent = $userAgent;
@@ -155,10 +162,10 @@ public function setUserAgent($userAgent)
     /**
      * Check user agent string against the regex.
      *
-     * @param  string|null  $userAgent
-     * @return bool
+     * @param string|null $userAgent User agent string to check
+     * @return bool True if crawler detected, false otherwise
      */
-    public function isCrawler($userAgent = null)
+    public function isCrawler(?string $userAgent = null): bool
     {
         $agent = trim(preg_replace(
             "/{$this->compiledExclusions}/i",
@@ -178,17 +185,19 @@ public function isCrawler($userAgent = null)
     /**
      * Return the matches.
      *
-     * @return string|null
+     * @return string|null The matched bot name or null if no match
      */
-    public function getMatches()
+    public function getMatches(): ?string
     {
         return isset($this->matches[0]) ? $this->matches[0] : null;
     }
 
     /**
-     * @return string|null
+     * Get the user agent string.
+     *
+     * @return string|null The user agent string
      */
-    public function getUserAgent()
+    public function getUserAgent(): ?string
     {
         return $this->userAgent;
     }
diff --git a/src/Fixtures/AbstractProvider.php b/src/Fixtures/AbstractProvider.php
index ffe10f5..1031b40 100644
--- a/src/Fixtures/AbstractProvider.php
+++ b/src/Fixtures/AbstractProvider.php
@@ -16,16 +16,16 @@ abstract class AbstractProvider
     /**
      * The data set.
      *
-     * @var array
+     * @var array<int, string>
      */
-    protected $data;
+    protected $data = [];
 
     /**
      * Return the data set.
      *
-     * @return array
+     * @return array<int, string> Array of data
      */
-    public function getAll()
+    public function getAll(): array
     {
         return $this->data;
     }
diff --git a/src/Fixtures/Crawlers.php b/src/Fixtures/Crawlers.php
index 6f70ab1..5c8f72f 100644
--- a/src/Fixtures/Crawlers.php
+++ b/src/Fixtures/Crawlers.php
@@ -16,7 +16,7 @@ class Crawlers extends AbstractProvider
     /**
      * Array of regular expressions to match against the user agent.
      *
-     * @var array
+     * @var array<int, string>
      */
     protected $data = [
         ' YLT',
diff --git a/src/Fixtures/Exclusions.php b/src/Fixtures/Exclusions.php
index 9717703..07cc4a9 100644
--- a/src/Fixtures/Exclusions.php
+++ b/src/Fixtures/Exclusions.php
@@ -17,7 +17,7 @@ class Exclusions extends AbstractProvider
      * List of strings to remove from the user agent before running the crawler regex
      * Over a large list of user agents, this gives us about a 55% speed increase!
      *
-     * @var array
+     * @var array<int, string>
      */
     protected $data = [
         'Safari.[\d\.]*',
diff --git a/src/Fixtures/Headers.php b/src/Fixtures/Headers.php
index 562f29a..a6c9d98 100644
--- a/src/Fixtures/Headers.php
+++ b/src/Fixtures/Headers.php
@@ -16,7 +16,7 @@ class Headers extends AbstractProvider
     /**
      * All possible HTTP headers that represent the user agent string.
      *
-     * @var array
+     * @var array<int, string>
      */
     protected $data = [
         // The default User-Agent string.
diff --git a/tests/UserAgentTest.php b/tests/UserAgentTest.php
index e2d7d26..9d45883 100644
--- a/tests/UserAgentTest.php
+++ b/tests/UserAgentTest.php
@@ -15,12 +15,13 @@
 
 final class UserAgentTest extends TestCase
 {
-    public $CrawlerDetect;
+    /** @var CrawlerDetect|null */
+    private $CrawlerDetect;
 
     /** @test */
-    public function user_agents_are_bots()
+    public function user_agents_are_bots(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $lines = file(__DIR__.'/data/user_agent/crawlers.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
 
         foreach ($lines as $line) {
@@ -30,9 +31,9 @@ public function user_agents_are_bots()
     }
 
     /** @test */
-    public function user_agents_are_devices()
+    public function user_agents_are_devices(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $lines = file(__DIR__.'/data/user_agent/devices.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
 
         foreach ($lines as $line) {
@@ -42,9 +43,9 @@ public function user_agents_are_devices()
     }
 
     /** @test */
-    public function sec_ch_ua_are_bots()
+    public function sec_ch_ua_are_bots(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $lines = file(__DIR__.'/data/sec_ch_ua/crawlers.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
 
         foreach ($lines as $line) {
@@ -54,9 +55,9 @@ public function sec_ch_ua_are_bots()
     }
 
     /** @test */
-    public function sec_ch_ua_are_devices()
+    public function sec_ch_ua_are_devices(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $lines = file(__DIR__.'/data/sec_ch_ua/devices.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
 
         foreach ($lines as $line) {
@@ -66,9 +67,9 @@ public function sec_ch_ua_are_devices()
     }
 
     /** @test */
-    public function it_returns_correct_matched_bot_name()
+    public function it_returns_correct_matched_bot_name(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $this->CrawlerDetect->isCrawler('Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X) AppleWebKit (KHTML, like Gecko) Mobile (compatible; Yahoo Ad monitoring; https://help.yahoo.com/kb/yahoo-ad-monitoring-SLN24857.html)');
 
         $matches = $this->CrawlerDetect->getMatches();
@@ -77,7 +78,7 @@ public function it_returns_correct_matched_bot_name()
     }
 
     /** @test */
-    public function it_returns_user_agent()
+    public function it_returns_user_agent(): void
     {
         $ua = 'Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X) AppleWebKit (KHTML, like Gecko) Mobile (compatible; Yahoo Ad monitoring; https://help.yahoo.com/kb/yahoo-ad-monitoring-SLN24857.html)';
         $this->CrawlerDetect = new CrawlerDetect(null, $ua);
@@ -86,9 +87,9 @@ public function it_returns_user_agent()
     }
 
     /** @test */
-    public function it_returns_full_matched_bot_name()
+    public function it_returns_full_matched_bot_name(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $this->CrawlerDetect->isCrawler('somenaughtybot');
 
         $matches = $this->CrawlerDetect->getMatches();
@@ -97,25 +98,25 @@ public function it_returns_full_matched_bot_name()
     }
 
     /** @test */
-    public function it_returns_null_when_no_bot_detected()
+    public function it_returns_null_when_no_bot_detected(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $this->CrawlerDetect->isCrawler('nothing to see here');
 
         $this->assertNull($this->CrawlerDetect->getMatches());
     }
 
     /** @test */
-    public function empty_user_agent()
+    public function empty_user_agent(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $test = $this->CrawlerDetect->isCrawler('      ');
 
         $this->assertFalse($test);
     }
 
     /** @test */
-    public function current_visitor()
+    public function current_visitor(): void
     {
         $headers = (array) json_decode('{"DOCUMENT_ROOT":"\/home\/test\/public_html","GATEWAY_INTERFACE":"CGI\/1.1","HTTP_ACCEPT":"*\/*","HTTP_ACCEPT_ENCODING":"gzip, deflate","HTTP_CACHE_CONTROL":"no-cache","HTTP_CONNECTION":"Keep-Alive","HTTP_FROM":"bingbot(at)microsoft.com","HTTP_HOST":"www.test.com","HTTP_PRAGMA":"no-cache","HTTP_USER_AGENT":"Mozilla\/5.0 (compatible; bingbot\/2.0; +http:\/\/www.bing.com\/bingbot.htm)","PATH":"\/bin:\/usr\/bin","QUERY_STRING":"order=closingDate","REDIRECT_STATUS":"200","REMOTE_ADDR":"127.0.0.1","REMOTE_PORT":"3360","REQUEST_METHOD":"GET","REQUEST_URI":"\/?test=testing","SCRIPT_FILENAME":"\/home\/test\/public_html\/index.php","SCRIPT_NAME":"\/index.php","SERVER_ADDR":"127.0.0.1","SERVER_ADMIN":"webmaster@test.com","SERVER_NAME":"www.test.com","SERVER_PORT":"80","SERVER_PROTOCOL":"HTTP\/1.1","SERVER_SIGNATURE":"","SERVER_SOFTWARE":"Apache","UNIQUE_ID":"Vx6MENRxerBUSDEQgFLAAAAAS","PHP_SELF":"\/index.php","REQUEST_TIME_FLOAT":1461619728.0705,"REQUEST_TIME":1461619728}');
 
@@ -125,7 +126,7 @@ public function current_visitor()
     }
 
     /** @test */
-    public function user_agent_passed_via_contructor()
+    public function user_agent_passed_via_contructor(): void
     {
         $cd = new CrawlerDetect(null, 'Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X) AppleWebKit (KHTML, like Gecko) Mobile (compatible; Yahoo Ad monitoring; https://help.yahoo.com/kb/yahoo-ad-monitoring-SLN24857.html)');
 
@@ -133,7 +134,7 @@ public function user_agent_passed_via_contructor()
     }
 
     /** @test */
-    public function http_from_header()
+    public function http_from_header(): void
     {
         $headers = (array) json_decode('{"DOCUMENT_ROOT":"\/home\/test\/public_html","GATEWAY_INTERFACE":"CGI\/1.1","HTTP_ACCEPT":"*\/*","HTTP_ACCEPT_ENCODING":"gzip, deflate","HTTP_CACHE_CONTROL":"no-cache","HTTP_CONNECTION":"Keep-Alive","HTTP_FROM":"googlebot(at)googlebot.com","HTTP_HOST":"www.test.com","HTTP_PRAGMA":"no-cache","HTTP_USER_AGENT":"Mozilla\/5.0 (Macintosh; Intel Mac OS X 10_8_4) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/28.0.1500.71 Safari\/537.36","PATH":"\/bin:\/usr\/bin","QUERY_STRING":"order=closingDate","REDIRECT_STATUS":"200","REMOTE_ADDR":"127.0.0.1","REMOTE_PORT":"3360","REQUEST_METHOD":"GET","REQUEST_URI":"\/?test=testing","SCRIPT_FILENAME":"\/home\/test\/public_html\/index.php","SCRIPT_NAME":"\/index.php","SERVER_ADDR":"127.0.0.1","SERVER_ADMIN":"webmaster@test.com","SERVER_NAME":"www.test.com","SERVER_PORT":"80","SERVER_PROTOCOL":"HTTP\/1.1","SERVER_SIGNATURE":"","SERVER_SOFTWARE":"Apache","UNIQUE_ID":"Vx6MENRxerBUSDEQgFLAAAAAS","PHP_SELF":"\/index.php","REQUEST_TIME_FLOAT":1461619728.0705,"REQUEST_TIME":1461619728}');
 
@@ -143,9 +144,9 @@ public function http_from_header()
     }
 
     /** @test */
-    public function matches_does_not_persit_across_multiple_calls()
+    public function matches_does_not_persit_across_multiple_calls(): void
     {
-        $this->CrawlerDetect = new CrawlerDetect;
+        $this->CrawlerDetect = new CrawlerDetect();
         $this->CrawlerDetect->isCrawler('Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X) AppleWebKit (KHTML, like Gecko) Mobile (compatible; Yahoo Ad monitoring; https://help.yahoo.com/kb/yahoo-ad-monitoring-SLN24857.html)');
         $matches = $this->CrawlerDetect->getMatches();
         $this->assertEquals($this->CrawlerDetect->getMatches(), 'monitoring', $matches);
@@ -166,17 +167,17 @@ public function matches_does_not_persit_across_multiple_calls()
     }
 
     /** @test */
-    public function the_regex_patterns_are_unique()
+    public function the_regex_patterns_are_unique(): void
     {
-        $crawlers = new Crawlers;
+        $crawlers = new Crawlers();
 
         $this->assertEquals(count($crawlers->getAll()), count(array_unique($crawlers->getAll())));
     }
 
     /** @test */
-    public function there_are_no_regex_collisions()
+    public function there_are_no_regex_collisions(): void
     {
-        $crawlers = new Crawlers;
+        $crawlers = new Crawlers();
 
         foreach ($crawlers->getAll() as $key1 => $regex) {
             foreach ($crawlers->getAll() as $key2 => $compare) {