src/HttpHandler.php
public function pushHeader(string $key, string $value = null)
	{
		$headers = $this->getHeaders();

		$headers[$key] = $value;

		$this->setHeaders($headers);

		return $this;
	}
public function pushHeader(string $key, string $value = null)
	{
		$headers = $this->getHeaders();

		$headers[$key] = $value;

		$this->setHeaders($headers);

		return $this;
	}
public function pushHeader ( string $ key , string $ value = null ) { $ headers = $ this -> getHeaders ( ) ; $ headers [ $ key ] = $ value ; $ this -> setHeaders ( $ headers ) ; return $ this ; }
Pushes a header value onto the headers array.

@param  string      $key   The header key.
@param  string|null $value The header value.
@return self
Pushes a header value onto the headers array .