What is PSR-7

PSR-7 is a set of common interfaces defined by PHP Framework Interop Group. These interfaces are representing HTTP messages, and URIs for use when communicating trough HTTP.

HTTP messages are the foundation of web development. Web browsers and HTTP clients such as cURL create HTTP request messages that are sent to a web server, which provides an HTTP response message. Server-side code receives an HTTP request message, and returns an HTTP response message.

HTTP messages are typically abstracted from the end-user consumer, but as developers, we typically need to know how they are structured and how to access or manipulate them in order to perform our tasks, whether that might be making a request to an HTTP API, or handling an incoming request.

source: PSR-7: HTTP message interfaces


In this section the Interfaces methods will be listed. The purpose of this list is to help in finding the methods when working with PSR-7. This can be considered as a cheatsheet for PSR-7 interfaces. The interfaces defined in PSR-7 are the following:

Class Name Description
Psr\Http\Message\MessageInterface Representation of a HTTP message
Psr\Http\Message\RequestInterface Representation of an outgoing, client-side request.
Psr\Http\Message\ServerRequestInterface Representation of an incoming, server-side HTTP request.
Psr\Http\Message\ResponseInterface Representation of an outgoing, server-side response.
Psr\Http\Message\StreamInterface Describes a data stream
Psr\Http\Message\UriInterface Value object representing a URI.
Psr\Http\Message\UploadedFileInterface Value object representing a file uploaded through an HTTP request.

Psr\Http\Message\MessageInterface Methods

Method Name Description Notes
getProtocolVersion() Gets HTTP protocol version 1.0 or 1.1
withProtocolVersion($version) Sets HTTP protocol version  
getHeaders() Gets all HTTP Headers Request Header List, Response Header List
hasHeader($name) Checks if HTTP Header with given name exists  
getHeader($name) Retrieves a array with the values for a single header  
getHeaderLine($name) Retrieves a comma-separated string of the values for a single header  
withHeader($name, $value) Sets a HTTP Header If header already exists, value will be overwritten
withAddedHeader($name, $value) Appends value to given header If header already exists value will be appended, if not a new header will be created
withoutHeader($name) Removes HTTP Header with given name  
getBody() Get the HTTP Message Body Returns object implementing StreamInterface
withBody(StreamInterface $body) Sets the HTTP Message Body  

Psr\Http\Message\RequestInterface Methods

Same methods as Psr\Http\Message\MessageInterface + the following methods:

Method Name Description Notes
getRequestTarget() Retrieves the message’s request target origin-form, absolute-form, authority-form, asterisk-form (RFC7230)
withRequestTarget($requestTarget) Return an instance with the specific request-target  
getMethod() Retrieves the HTTP method of the request. GET, HEAD, POST, PUT, DELETE, CONNECT, OPTIONS, TRACE (defined in RFC7231), PATCH (defined in RFC5789)
withMethod($method) Return an instance with the provided HTTP method  
getUri() Retrieves the URI instance  
withUri(UriInterface $uri, $preserveHost = false) Returns an instance with the provided URI  

Psr\Http\Message\ServerRequestInterface Methods

Same methods as Psr\Http\Message\RequestInterface + the following methods:

Method Name Description Notes
getServerParams() Retrieve server parameters Typically derived from $_SERVER
getCookieParams() Retrieves cookies sent by the client to the server. Typically derived from $_COOKIES
withCookieParams(array $cookies) Return an instance with the specified cookies  
withQueryParams(array $query) Return an instance with the specified query string arguments  
getUploadedFiles() Retrieve normalized file upload data  
withUploadedFiles(array $uploadedFiles) Create a new instance with the specified uploaded files  
getParsedBody() Retrieve any parameters provided in the request body  
withParsedBody($data) Return an instance with the specified body parameters  
getAttributes() Retrieve attributes derived from the request  
getAttribute($name, $default = null) Retrieve a single derived request attribute  
withAttribute($name, $value) Return an instance with the specified derived request attribute  
withoutAttribute($name) Return an instance that removes the specified derived request attribute  

Psr\Http\Message\ResponseInterface Methods

Same methods as Psr\Http\Message\MessageInterface + the following methods:

Method Name Description Notes
getStatusCode() Gets the response status code.  
withStatus($code, $reasonPhrase = '') Return an instance with the specified status code and, optionally, reason phrase.  
getReasonPhrase() Gets the response reason phrase associated with the status code.  

Psr\Http\Message\StreamInterface Methods

Method Name Description Notes
__toString() Reads all data from the stream into a string, from the beginning to end.  
close() Closes the stream and any underlying resources.  
detach() Separates any underlying resources from the stream.  
getSize() Get the size of the stream if known.  
eof() Returns true if the stream is at the end of the stream.  
isSeekable() Returns whether or not the stream is seekable.  
seek($offset, $whence = SEEK_SET) Seek to a position in the stream.  
rewind() Seek to the beginning of the stream.  
isWritable() Returns whether or not the stream is writable.  
write($string) Write data to the stream.  
isReadable() Returns whether or not the stream is readable.  
read($length) Read data from the stream.  
getContents() Returns the remaining contents in a string  
getMetadata($key = null)() Get stream metadata as an associative array or retrieve a specific key.  

Psr\Http\Message\UriInterface Methods

Method Name Description Notes
getScheme() Retrieve the scheme component of the URI.  
getAuthority() Retrieve the authority component of the URI.  
getUserInfo() Retrieve the user information component of the URI.  
getHost() Retrieve the host component of the URI.  
getPort() Retrieve the port component of the URI.  
getPath() etrieve the path component of the URI.  
getQuery() Retrieve the query string of the URI.  
getFragment() Retrieve the fragment component of the URI.  
withScheme($scheme) Return an instance with the specified scheme.  
withUserInfo($user, $password = null) Return an instance with the specified user information.  
withHost($host) Return an instance with the specified host.  
withPort($port) Return an instance with the specified port.  
withPath($path) Return an instance with the specified path.  
withQuery($query) Return an instance with the specified query string.  
withFragment($fragment) Return an instance with the specified URI fragment.  
__toString() Return the string representation as a URI reference.  


Method Name Description Notes
getStream() Retrieve a stream representing the uploaded file.  
moveTo($targetPath) Move the uploaded file to a new location.  
getSize() Retrieve the file size.  
getError() Retrieve the error associated with the uploaded file.  
getClientFilename() Retrieve the filename sent by the client.  
getClientMediaType() Retrieve the media type sent by the client.  

PSR-7 Usage

All PSR-7 applications comply with these interfaces They were created to establish a standard between middleware implementations.

RequestInterface, ServerRequestInterface, ResponseInterface extend MessageInterface because the Request and the Response are HTTP Messages. When using ServerRequestInterface, both RequestInterface and Psr\Http\Message\MessageInterface methods are considered.

The following examples will illustrate how basic operations are done in PSR-7.

Examples (using Zend Diactoros)

Zend Diactoros is an implementation for PSR-7 interfaces. It will be used to illustrate these examples. Installation guide for Zend Diactoros: Zend Diactoros Documentation - Installation

All other PSR-7 implementations should have the same behaviour.

To use the Zend Diactoros classes add this at the beggining of the php file:


use Zend\Diactoros\ServerRequestFactory;
use Zend\Diactoros\Response;

// autoloading

$request = ServerRequestFactory::fromGlobals($_SERVER, $_GET, $_POST, $_COOKIE, $_FILES);
$response = new Response();

Working with HTTP Headers

Adding headers to response

$response->withHeader('My-Custom-Header', 'My Custom Message');

Appending values to headers

$response->withAddedHeader('My-Custom-Header', 'The second message');

Checking if header exists

$request->hasHeader('My-Custom-Header'); // will return false
$response->hasHeader('My-Custom-Header'); // will return true

Note: My-Custom-Header was only added in the Response

Getting comma-separated values from a header (also applies to request)

// getting value from request headers
$request->getHeaderLine('Content-Type'); // will return: "text/html; charset=UTF-8"
// getting value from response headers
$response->getHeaderLine('My-Custom-Header'); // will return:  "My Custom Message; The second message"

Getting array of value from a header (also applies to request)

// getting value from request headers
$request->getHeader('Content-Type'); // will return: ["text/html", "charset=UTF-8"]
// getting value from response headers
$response->getHeader('My-Custom-Header'); // will return:  ["My Custom Message",  "The second message"]

Removing headers from HTTP Messages

// removing a header from Request, removing deprecated "Content-MD5" header

// removing a header from Response
// effect: the browser won't know the size of the stream
// the browser will download the stream till it ends

Working with HTTP Message Body

When working with the PSR-7 there are two methods of implementation:

1. Getting the body separately

This method makes the body handling easier to understand and is useful when repeatedly calling body methods. (You only call getBody() once). Using this method mistakes like $response->write() are also prevented.

$body = $response->getBody();
// operations on body, eg. read, write, seek
// ...
// replacing the old body
// this last statement is optional as we working with objects
// in this case the "new" body is same with the "old" one
// the $body variable has the same value as the one in $request, only the reference is passed

2. Working directly on response

This method is useful when only performing few operations as the $request->getBody() statement fragment is required


Getting the body contents

The following snippet gets the contents of a stream contents.

Note: Streams must be rewinded, if content was written into streams, it will be ignored when calling getContents() because the stream pointer is set to the last character, which is \0 - meaning end of stream.

$body = $response->getBody();
$body->rewind(); // or $body->seek(0);
$bodyText = $body->getContends();

Note: If $body->seek(1) is called before $body->getContents(), the first character will be ommited as the starting pointer is set to 1, not 0. This is why using $body->rewind() is recommended.

Append to body

$response->getBody()->write('Hello'); // writing directly
$body = $request->getBody(); // which is a `StreamInterface`

Prepend to body

Prepending is different when it comes to streams. The content must be copied before writing the content to be prepended. The following example will explain the behaviour of streams.

// assuming our response is initially empty
$body = $repsonse->getBody();
// writing the string "abcd"

// seeking to start of stream
// writing 'ef'
$body->write('ef'); // at this point the stream contains "efcd"

Prepending by rewriting separately

// assuming our response body stream only contains: "abcd"
$body = $response->getBody();
$contents = $body->getContents(); // abcd
// seeking the stream to beginning
$body->write('ef'); // stream contains "efcd"
$body->write($contents); // stream contains "efabcd"

Note: getContents() seeks the stream while reading it, therefore if the second rewind() method call was not present the stream would have resulted in abcdefabcd because the write() method appends to stream if not preceeded by rewind() or seek(0).

Prepending by using contents as a string

$body = $response->getBody();
$contents = $body->getContents(); // efabcd
$contents = 'ef'.$contents;

Sources: PSR-7: HTTP messages zend-diactoros

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