src/Headers.php
public function push($headers, $value = '')
    {
        if (is_string($headers) && func_num_args() === 2) {
            $headers = [$headers => $value];
        }
        return $this->_set($headers);
    }
public function push($headers, $value = '')
    {
        if (is_string($headers) && func_num_args() === 2) {
            $headers = [$headers => $value];
        }
        return $this->_set($headers);
    }
public function push ( $ headers , $ value = '' ) { if ( is_string ( $ headers ) && func_num_args ( ) === 2 ) { $ headers = [ $ headers => $ value ] ; } return $ this -> _set ( $ headers ) ; }
Sets some headers.

@param  string|array $headers A header name, string content or an array of headers.
@param  string|array $value   The header value. I set, `$headers` must be an header string name.
@return self
Sets some headers .