PSR7-Usage

PSR-7 UsageAll 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.ExamplesFor this examples to work (at least) a PSR-7 implementation package is required. (eg: zendframework/zend-diactoros, guzzlehttp/psr7, slim/slim, etc)All PSR-7 implementations should have the same behaviour.The following will be assumed: `$request` is an object of `Psr\Http\Message\RequestInterface` and`$response` is an object implementing `Psr\Http\Message\RequestInterface`Working with HTTP HeadersAdding 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 ResponseGetting 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 $request->withoutHeader('Content-MD5'); // 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 $response->withoutHeader('Content-Length'); Working with HTTP Message BodyWhen working with the PSR-7 there are two methods of implementation:1. Getting the body separatelyThis method makes the body handling easier to understand and is useful when repeatedly calling body methods. (You only call `getBody()` once). Using this method mistakes like `$response->write()` are also prevented.$body = $response->getBody(); // operations on body, eg. read, write, seek // ... // replacing the old body $response->withBody($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 $request, only the reference is passed 2. Working directly on responseThis method is useful when only performing few operations as the `$request->getBody()` statement fragment is required$response->getBody()->write('hello'); Getting the body contentsThe following snippet gets the contents of a stream contents.Note: Streams must be rewinded, if content was written into streams, it will be ignored when calling `getContents()` because the stream pointer is set to the last character, which is `\0` - meaning end of stream.$body = $response->getBody(); $body->rewind(); // or $body->seek(0); $bodyText = $body->getContents(); Note: If `$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` $body->write('xxxxx'); Prepend to bodyPrepending 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" $body->write('abcd'); // seeking to start of stream $body->seek(0); // 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(); $body->rewind(); $contents = $body->getContents(); // abcd // seeking the stream to beginning $body->rewind(); $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(); $body->rewind(); $contents = $body->getContents(); // efabcd $contents = 'ef'.$contents; $body->rewind(); $body->write($contents);