original_string: public function getHeader($key)
      {
          foreach ($this->headers as $header => $content) {
              if (strtolower($key) === strtolower($header)) {
                  return $content;
              }
          }
          return null;
      }
code: public function getHeader($key)
      {
          foreach ($this->headers as $header => $content) {
              if (strtolower($key) === strtolower($header)) {
                  return $content;
              }
          }
          return null;
      }
code_tokens: public function getHeader ( $ key ) { foreach ( $ this -> headers as $ header => $ content ) { if ( strtolower ( $ key ) === strtolower ( $ header ) ) { return $ content ; } } return null ; }
docstring: Return header by key if it exists.
  
  @param string $key
  
  @return null|string
docstring_tokens: Return header by key if it exists .