improve code

Author: fenric

src/HeaderDate.php

@@ -14,6 +14,7 @@
 /**
  * Import classes
  */
+use DateTime;
 use DateTimeInterface;
 use DateTimeZone;
 
@@ -82,6 +83,6 @@ public function getFieldValue() : string
     {
         $this->getTimestamp()->setTimezone(new DateTimeZone('GMT'));
 
-        return $this->getTimestamp()->format(DateTimeInterface::RFC822);
+        return $this->getTimestamp()->format(DateTime::RFC822);
     }
 }

src/HeaderExpires.php

@@ -14,6 +14,7 @@
 /**
  * Import classes
  */
+use DateTime;
 use DateTimeInterface;
 use DateTimeZone;
 
@@ -82,6 +83,6 @@ public function getFieldValue() : string
     {
         $this->getTimestamp()->setTimezone(new DateTimeZone('GMT'));
 
-        return $this->getTimestamp()->format(DateTimeInterface::RFC822);
+        return $this->getTimestamp()->format(DateTime::RFC822);
     }
 }

src/HeaderLastModified.php

@@ -14,6 +14,7 @@
 /**
  * Import classes
  */
+use DateTime;
 use DateTimeInterface;
 use DateTimeZone;
 
@@ -82,6 +83,6 @@ public function getFieldValue() : string
     {
         $this->getTimestamp()->setTimezone(new DateTimeZone('GMT'));
 
-        return $this->getTimestamp()->format(DateTimeInterface::RFC822);
+        return $this->getTimestamp()->format(DateTime::RFC822);
     }
 }

src/HeaderRetryAfter.php

@@ -14,6 +14,7 @@
 /**
  * Import classes
  */
+use DateTime;
 use DateTimeInterface;
 use DateTimeZone;
 
@@ -82,6 +83,6 @@ public function getFieldValue() : string
     {
         $this->getTimestamp()->setTimezone(new DateTimeZone('GMT'));
 
-        return $this->getTimestamp()->format(DateTimeInterface::RFC822);
+        return $this->getTimestamp()->format(DateTime::RFC822);
     }
 }

src/HeaderSetCookie.php

@@ -14,6 +14,7 @@
 /**
  * Import classes
  */
+use DateTime;
 use DateTimeInterface;
 use DateTimeZone;
 use InvalidArgumentException;
@@ -375,7 +376,7 @@ public function getFieldValue() : string
         if ($this->getExpires() instanceof DateTimeInterface) {
             $this->getExpires()->setTimezone(new DateTimeZone('GMT'));
 
-            $result .= '; Expires=' . $this->getExpires()->format(DateTimeInterface::RFC822);
+            $result .= '; Expires=' . $this->getExpires()->format(DateTime::RFC822);
             $result .= '; Max-Age=' . ($this->getExpires()->getTimestamp() - time());
         }
 

src/HeaderSunset.php

@@ -14,6 +14,7 @@
 /**
  * Import classes
  */
+use DateTime;
 use DateTimeInterface;
 use DateTimeZone;
 
@@ -82,6 +83,6 @@ public function getFieldValue() : string
     {
         $this->getTimestamp()->setTimezone(new DateTimeZone('GMT'));
 
-        return $this->getTimestamp()->format(DateTimeInterface::RFC822);
+        return $this->getTimestamp()->format(DateTime::RFC822);
     }
 }

src/HeaderWarning.php

@@ -14,6 +14,7 @@
 /**
  * Import classes
  */
+use DateTime;
 use DateTimeInterface;
 use DateTimeZone;
 use InvalidArgumentException;
@@ -226,7 +227,7 @@ public function getFieldValue() : string
         if ($this->getDate() instanceof DateTimeInterface) {
             $this->getDate()->setTimezone(new DateTimeZone('GMT'));
 
-            $result .= ' "' . $this->getDate()->format(DateTimeInterface::RFC822) . '"';
+            $result .= ' "' . $this->getDate()->format(DateTime::RFC822) . '"';
         }
 
         return $result;