What is the meaning of colon (:) operator after member function name in php [duplicate]

Question

I want to know the meaning of colon after method name i.e.

public function getTitle():Data {

interface Data { 
     public function details(string $name);
}
class Company {
     private $title;

     public function getTitle():Data {
      return $this->title;
     }

     public function setTitle(Data $title)
     {
      $this->title=$title
     }

}

.....
.....

Answer 1

public function getTitle():Data {
     return $this->title;
}

"Return type declaration" added since PHP 7.0 (This method should return an object having type "Data").

Like "Argument type declaration", "Return type declaration" is optional.

to check the new features introduced in PHP 7.0

check this link http://php.net/manual/en/migration70.new-features.php