replace call_user_func* with self invoked function

src/Transport/File.php

@@ -71,7 +71,7 @@ public function setOptions(FileOptions $options)
     public function send(Message $message)
     {
         $options  = $this->options;
-        $filename = call_user_func($options->getCallback(), $this);
+        $filename = $options->getCallback()($this);
         $file     = $options->getPath() . DIRECTORY_SEPARATOR . $filename;
         $email    = $message->toString();
 

src/Transport/Sendmail.php

@@ -134,7 +134,7 @@ public function send(Mail\Message $message)
             $headers = str_replace("\r\n", "\n", $headers);
         }
 
-        call_user_func($this->callable, $to, $subject, $body, $headers, $params);
+        ($this->callable)($to, $subject, $body, $headers, $params);
     }
 
     /**

test/Header/AddressListHeaderTest.php

@@ -118,7 +118,7 @@ public function getStringHeaders()
     public function testDeserializationFromString($headerLine, $class)
     {
         $callback = sprintf('%s::fromString', $class);
-        $header   = call_user_func($callback, $headerLine);
+        $header   = $callback($headerLine);
         $this->assertInstanceOf($class, $header);
         $list = $header->getAddressList();
         $this->assertEquals(4, count($list));
@@ -175,7 +175,7 @@ public function getHeadersWithComments()
     public function testAllowsNoWhitespaceBetweenHeaderAndValue($headerLine, $class)
     {
         $callback = sprintf('%s::fromString', $class);
-        $header   = call_user_func($callback, $headerLine);
+        $header   = $callback($headerLine);
         $this->assertInstanceOf($class, $header);
         $list = $header->getAddressList();
         $this->assertEquals(4, count($list));

test/Transport/FileOptionsTest.php

@@ -32,7 +32,7 @@ public function testDefaultCallbackIsSetByDefault()
     {
         $callback = $this->options->getCallback();
         $this->assertInternalType('callable', $callback);
-        $test     = call_user_func($callback, '');
+        $test     = $callback('');
         $this->assertRegExp('#^ZendMail_\d+_\d+\.eml$#', $test);
     }