public function exists($name, $offset = 0)
    {
        $s = $this->getNormalizedHeaderName($name);
        return isset($this->headerMap[$s][$offset]);
    }
public function exists($name, $offset = 0)
    {
        $s = $this->getNormalizedHeaderName($name);
        return isset($this->headerMap[$s][$offset]);
    }
public function exists ( $ name , $ offset = 0 ) { $ s = $ this -> getNormalizedHeaderName ( $ name ) ; return isset ( $ this -> headerMap [ $ s ] [ $ offset ] ) ; }
Returns true if the passed header exists in this collection.

@param string $name
@param int $offset
@return boolean
Returns true if the passed header exists in this collection .