HTTP Messages

The Message class provides an interface to the portions of an HTTP message that are common to both requests and responses, including the message body, protocol version, utilities for working with the headers, and methods for handling content negotiation.

This class is the parent class that both the Request Class and the Response Class extend from. As such, some methods, such as the content negotiation methods, may apply only to a request or response, and not the other one, but they have been included here to keep the header methods together.

What is Content Negotiation?

At it’s heart Content Negotiation is simply a part of the HTTP specification that allows a single resource to serve more than one type of content, allowing the clients to request the type of data that works best for them.

A classic example of this is a browser than cannot display PNG files can request only GIF or JPEG images. When the getServer receives the request, it looks at the available file types the client is requesting and selects the best match from the image formats that it supports, in this case likely choosing a JPEG image to return.

This same negotiation can happen with four types of data:

  • Media/Document Type - this could be image format, or HTML vs. XML or JSON.
  • Character Set - The character set the returned document should be set in. Typically is UTF-8.
  • Document Encoding - Typically the type of compression used on the results.
  • Document Language - For sites that support multiple languages, this helps determine which to return.

Class Reference

CodeIgniter\HTTP\Message
body()
Returns:The current message body
Return type:string

Returns the current message body, if any has been set. If not body exists, returns null:

echo $message->body();
setBody([$str])
Parameters:
  • $str (string) – The body of the message.
Returns:

the Message instance to allow methods to be chained together.

Return type:

CodeIgniter\HTTP\Message instance.

Sets the body of the current request.

populateHeaders()
Returns:void

Scans and parses the headers found in the SERVER data and stores it for later access. This is used by the IncomingRequest Class to make the current request’s headers available.

The headers are any SERVER data that starts with HTTP_, like HTTP_HOST. Each message is converted from it’s standard uppercase and underscore format to a ucwords and dash format. The preceding HTTP_ is removed from the string. So HTTP_ACCEPT_LANGUAGE becomes Accept-Language.

headers()
Returns:An array of all of the headers found.
Return type:array

Returns an array of all headers found or previously set.

Parameters:
  • $name (string) – The name of the header you want to retrieve the value of.
  • $filter (int) – The type of filter to apply. A list of filters can be found here.
Returns:

The current value of the header. If the header has multiple values, they will be returned as an array.

Return type:

string|array|null

Allows you to retrieve the current value of a single message header. $name is the case-insensitive header name. While the header is converted internally as described above, you can access the header with any type of case:

// These are all the same:
$message->header('HOST');
$message->header('Host');
$message->header('host');

If the header has multiple values, the values will return as an array of values. You can use the headerLine() method to retrieve the values as a string:

echo $message->header('Accept-Language');

// Outputs something like:
[
        'en',
        'en-US'
]

You can filter the header by passing a filter value in as the second parameter:

$message->header('Document-URI', FILTER_SANITIZE_URL);
headerLine($name)
Parameters:
  • $name (string) – The name of the header to retrieve.
Returns:

A string representing the header value.

Return type:

string

Returns the value(s) of the header as a string. This method allows you to easily get a string representation of the header values when the header has multiple values. The values are appropriately joined:

echo $message->headerLine('Accept-Language');

// Outputs:
en, en-US
setHeader([$name[, $value]])
Parameters:
  • $name (string) – The name of the header to set the value for.
  • $value (mixed) – The value to set the header to.
Returns:

The current message instance

Return type:

CodeIgniter\HTTP\Message

Sets the value of a single header. $name is the case-insensitive name of the header. If the header doesn’t already exist in the collection, it will be created. The $value can be either a string or an array of strings:

$message->setHeader('Host', 'codeigniter.com');
removeHeader([$name])
Parameters:
  • $name (string) – The name of the header to remove.
Returns:

The current message instance

Return type:

CodeIgniter\HTTP\Message

Removes the header from the Message. $name is the case-insensitive name of the header:

$message->remove('Host');
appendHeader([$name[, $value]]))
Parameters:
  • $name (string) – The name of the header to modify
  • $value (mixed) – The value to add to the header.
Returns:

The current message instance

Return type:

CodeIgniter\HTTP\Message

Adds a value to an existing header. The header must already be an array of values instead of a single string. If it is a string then a LogicException will be thrown.

$message->appendHeader('Accept-Language', 'en-US; q=0.8');
protocolVersion()
Returns:The current HTTP protocol version
Return type:string

Returns the message’s current HTTP protocol. If none has been set, will return null. Acceptable values are 1.0 and 1.1.

setProtocolVersion($version)
Parameters:
  • $version (string) – The HTTP protocol version
Returns:

The current message instance

Return type:

CodeIgniter\HTTP\Message

Sets the HTTP protocol version this Message uses. Valid values are 1.0 or 1.1:

$message->setProtocolVersion('1.1');
negotiateMedia($supported[, $strictMatch=false])
Parameters:
  • $supported (array) – An array of media types the application supports
  • $strictMatch (bool) – Whether it should force an exact match to happen.
Returns:

The supported media type that best matches what is requested.

Return type:

string

Parses the Accept header and compares with the application’s supported media types to determine the best match. Returns the appropriate media type. The first parameter is an array of application supported media types that should be compared against header values:

$supported = [
        'image/png',
        'image/jpg',
        'image/gif'
];
$imageType = $message->negotiateMedia($supported);

The $supported array should be structured so that the application’s preferred format is the first in the array, with the rest following in descending order of priority. If no match can be made between the header values and the supported values, the first element of the array will be returned.

Per the RFC the match has the option of returning a default value, like this method does, or to return an empty string. If you need to have an exact match and would like an empty string returned instead, pass true as the second parameter:

// Returns empty string if no match.
$imageType = $message->negotiateMedia($supported, true);

The matching process takes into account the priorities and specificity of the RFC. This means that the more specific header values will have a higher order of precedence, unless modified by a different q value. For more details, please read the appropriate section of the RFC.

negotiateCharset($supported)
Parameters:
  • $supported (array) – An array of character sets the application supports.
Returns:

The supported character set that best matches what is required..

Return type:

string

This is used identically to the negotiateMedia() method, except that it matches against the Accept-Charset header string:

$supported = [
        'utf-8',
        'iso-8895-9'
];
$charset = $message->negotiateCharset($supported);

If no match is found, the system will default to utf-8.

negotiateEncoding($supported)
Parameters:
  • $supported (array) – An array of character encodings the application supports.
Returns:

The supported character set that best matches what is required..

Return type:

string

Determines the best match between the application-supported values and the Accept-Encoding header value. If no match is found, will return the first element of the $supported array:

$supported = [
        'gzip',
        'compress'
];
$encoding = $message->negotiateEncoding($supported);
negotiateLanguage($supported)
Parameters:
  • $supported (array) – An array of languages the application supports.
Returns:

The supported language that best matches what is required..

Return type:

string

Determines the best match between the application-supported languages and the Accept-Language header value. If no match is found, will return the first element of the $supported array:

$supported = [
        'en',
        'fr',
        'x-pig-latin'
];
$language = $message->negotiateLanguage($supported);

More information about the language tags are available in RFC 1766.