diff --git a/AbstractBrowser.php b/AbstractBrowser.php
index 60f2fcb1..f8c89871 100644
--- a/AbstractBrowser.php
+++ b/AbstractBrowser.php
@@ -352,12 +352,12 @@ public function request(string $method, string $uri, array $parameters = [], arr
 
         $server = array_merge($this->server, $server);
 
-        if (!empty($server['HTTP_HOST']) && null === parse_url($originalUri, PHP_URL_HOST)) {
+        if (!empty($server['HTTP_HOST']) && null === parse_url($originalUri, \PHP_URL_HOST)) {
             $uri = preg_replace('{^(https?\://)'.preg_quote($this->extractHost($uri)).'}', '${1}'.$server['HTTP_HOST'], $uri);
         }
 
-        if (isset($server['HTTPS']) && null === parse_url($originalUri, PHP_URL_SCHEME)) {
-            $uri = preg_replace('{^'.parse_url($uri, PHP_URL_SCHEME).'}', $server['HTTPS'] ? 'https' : 'http', $uri);
+        if (isset($server['HTTPS']) && null === parse_url($originalUri, \PHP_URL_SCHEME)) {
+            $uri = preg_replace('{^'.parse_url($uri, \PHP_URL_SCHEME).'}', $server['HTTPS'] ? 'https' : 'http', $uri);
         }
 
         if (!isset($server['HTTP_REFERER']) && !$this->history->isEmpty()) {
@@ -368,7 +368,7 @@ public function request(string $method, string $uri, array $parameters = [], arr
             $server['HTTP_HOST'] = $this->extractHost($uri);
         }
 
-        $server['HTTPS'] = 'https' == parse_url($uri, PHP_URL_SCHEME);
+        $server['HTTPS'] = 'https' == parse_url($uri, \PHP_URL_SCHEME);
 
         $this->internalRequest = new Request($uri, $method, $parameters, $files, $this->cookieJar->allValues($uri), $server, $content);
 
@@ -437,9 +437,9 @@ protected function doRequestInProcess($request)
             foreach ($deprecations ? unserialize($deprecations) : [] as $deprecation) {
                 if ($deprecation[0]) {
                     // unsilenced on purpose
-                    trigger_error($deprecation[1], E_USER_DEPRECATED);
+                    trigger_error($deprecation[1], \E_USER_DEPRECATED);
                 } else {
-                    @trigger_error($deprecation[1], E_USER_DEPRECATED);
+                    @trigger_error($deprecation[1], \E_USER_DEPRECATED);
                 }
             }
         }
@@ -653,7 +653,7 @@ protected function getAbsoluteUri(string $uri)
 
         // protocol relative URL
         if (0 === strpos($uri, '//')) {
-            return parse_url($currentUri, PHP_URL_SCHEME).':'.$uri;
+            return parse_url($currentUri, \PHP_URL_SCHEME).':'.$uri;
         }
 
         // anchor or query string parameters?
@@ -662,7 +662,7 @@ protected function getAbsoluteUri(string $uri)
         }
 
         if ('/' !== $uri[0]) {
-            $path = parse_url($currentUri, PHP_URL_PATH);
+            $path = parse_url($currentUri, \PHP_URL_PATH);
 
             if ('/' !== substr($path, -1)) {
                 $path = substr($path, 0, strrpos($path, '/') + 1);
@@ -689,7 +689,7 @@ protected function requestFromRequest(Request $request, $changeHistory = true)
     private function updateServerFromUri(array $server, string $uri): array
     {
         $server['HTTP_HOST'] = $this->extractHost($uri);
-        $scheme = parse_url($uri, PHP_URL_SCHEME);
+        $scheme = parse_url($uri, \PHP_URL_SCHEME);
         $server['HTTPS'] = null === $scheme ? $server['HTTPS'] : 'https' == $scheme;
         unset($server['HTTP_IF_NONE_MATCH'], $server['HTTP_IF_MODIFIED_SINCE']);
 
@@ -698,9 +698,9 @@ private function updateServerFromUri(array $server, string $uri): array
 
     private function extractHost(string $uri): ?string
     {
-        $host = parse_url($uri, PHP_URL_HOST);
+        $host = parse_url($uri, \PHP_URL_HOST);
 
-        if ($port = parse_url($uri, PHP_URL_PORT)) {
+        if ($port = parse_url($uri, \PHP_URL_PORT)) {
             return $host.':'.$port;
         }
 
diff --git a/HttpBrowser.php b/HttpBrowser.php
index ed6c1002..6f5749c2 100644
--- a/HttpBrowser.php
+++ b/HttpBrowser.php
@@ -91,7 +91,7 @@ private function getBodyAndExtraHeaders(Request $request, array $headers): array
             return ['', []];
         }
 
-        return [http_build_query($fields, '', '&', PHP_QUERY_RFC1738), ['Content-Type' => 'application/x-www-form-urlencoded']];
+        return [http_build_query($fields, '', '&', \PHP_QUERY_RFC1738), ['Content-Type' => 'application/x-www-form-urlencoded']];
     }
 
     private function getHeaders(Request $request): array