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PSR7-Usage.md
001 ### PSR-7 Usage
002
003 All PSR-7 applications comply with these interfaces
004 They were created to establish a standard between middleware implementations.
005
006 > `RequestInterface`, `ServerRequestInterface`, `ResponseInterface` extend `MessageInterface` because the `Request` and the `Response` are `HTTP Messages`.
007 > When using `ServerRequestInterface`, both `RequestInterface` and `Psr\Http\Message\MessageInterface` methods are considered.
008
009
010 The following examples will illustrate how basic operations are done in PSR-7.
011
012 ##### Examples
013
014
015 For this examples to work (at least) a PSR-7 implementation package is required. (eg: zendframework/zend-diactoros, guzzlehttp/psr7, slim/slim, etc)
016 All PSR-7 implementations should have the same behaviour.
017
018 The following will be assumed:
019 `$request` is an object of `Psr\Http\Message\RequestInterface` and
020
021 `$response` is an object implementing `Psr\Http\Message\RequestInterface`
022
023
024 ### Working with HTTP Headers
025
026 #### Adding headers to response:
027
028 ```php
029 $response->withHeader('My-Custom-Header', 'My Custom Message');
030 ```
031
032 #### Appending values to headers
033
034 ```php
035 $response->withAddedHeader('My-Custom-Header', 'The second message');
036 ```
037
038 #### Checking if header exists:
039
040 ```php
041 $request->hasHeader('My-Custom-Header'); // will return false
042 $response->hasHeader('My-Custom-Header'); // will return true
043 ```
044
045 > Note: My-Custom-Header was only added in the Response
046
047 #### Getting comma-separated values from a header (also applies to request)
048
049 ```php
050 // getting value from request headers
051 $request->getHeaderLine('Content-Type'); // will return: "text/html; charset=UTF-8"
052 // getting value from response headers
053 $response->getHeaderLine('My-Custom-Header'); // will return: "My Custom Message; The second message"
054 ```
055
056 #### Getting array of value from a header (also applies to request)
057 ```php
058 // getting value from request headers
059 $request->getHeader('Content-Type'); // will return: ["text/html", "charset=UTF-8"]
060 // getting value from response headers
061 $response->getHeader('My-Custom-Header'); // will return: ["My Custom Message", "The second message"]
062 ```
063
064 #### Removing headers from HTTP Messages
065 ```php
066 // removing a header from Request, removing deprecated "Content-MD5" header
067 $request->withoutHeader('Content-MD5');
068
069 // removing a header from Response
070 // effect: the browser won't know the size of the stream
071 // the browser will download the stream till it ends
072 $response->withoutHeader('Content-Length');
073 ```
074
075 ### Working with HTTP Message Body
076
077 When working with the PSR-7 there are two methods of implementation:
078 #### 1. Getting the body separately
079
080 > This method makes the body handling easier to understand and is useful when repeatedly calling body methods. (You only call `getBody()` once). Using this method mistakes like `$response->write()` are also prevented.
081
082 ```php
083 $body = $response->getBody();
084 // operations on body, eg. read, write, seek
085 // ...
086 // replacing the old body
087 $response->withBody($body);
088 // this last statement is optional as we working with objects
089 // in this case the "new" body is same with the "old" one
090 // the $body variable has the same value as the one in $request, only the reference is passed
091 ```
092
093 #### 2. Working directly on response
094
095 > This method is useful when only performing few operations as the `$request->getBody()` statement fragment is required
096
097 ```php
098 $response->getBody()->write('hello');
099 ```
100
101 ### Getting the body contents
102
103 The following snippet gets the contents of a stream contents.
104 > 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.
105 ```php
106 $body = $response->getBody();
107 $body->rewind(); // or $body->seek(0);
108 $bodyText = $body->getContents();
109 ```
110 > Note: If `$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.
111
112 ### Append to body
113
114 ```php
115 $response->getBody()->write('Hello'); // writing directly
116 $body = $request->getBody(); // which is a `StreamInterface`
117 $body->write('xxxxx');
118 ```
119
120 ### Prepend to body
121 Prepending is different when it comes to streams. The content must be copied before writing the content to be prepended.
122 The following example will explain the behaviour of streams.
123
124 ```php
125 // assuming our response is initially empty
126 $body = $repsonse->getBody();
127 // writing the string "abcd"
128 $body->write('abcd');
129
130 // seeking to start of stream
131 $body->seek(0);
132 // writing 'ef'
133 $body->write('ef'); // at this point the stream contains "efcd"
134 ```
135
136 #### Prepending by rewriting separately
137
138 ```php
139 // assuming our response body stream only contains: "abcd"
140 $body = $response->getBody();
141 $body->rewind();
142 $contents = $body->getContents(); // abcd
143 // seeking the stream to beginning
144 $body->rewind();
145 $body->write('ef'); // stream contains "efcd"
146 $body->write($contents); // stream contains "efabcd"
147 ```
148
149 > 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)`.
150
151 #### Prepending by using contents as a string
152 ```php
153 $body = $response->getBody();
154 $body->rewind();
155 $contents = $body->getContents(); // efabcd
156 $contents = 'ef'.$contents;
157 $body->rewind();
158 $body->write($contents);
159 ```
160