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28 ” HTTP Streams W rapper code (though it is more noticeable in a high load environment). On the negative side, you have to either kno w C or depend on the community to deliver patches in a timely fashion for any issues that may arise. This also applies to extensions written in C that will be co vered in subsequent sections. The streams wrapper is part of the PHP core and as such has no installation requirements beyond that of PHP itself. Simple R equest and R esponse H andling H ere’s a simple example of the HTTP streams wrapper in action. There are a few things to note. • The allow_url_fopen PHP configuration setting must be enabled for this to work, which it is in most environments. • In this example, the file_get_contents function call is equivalent to making a GET request for the specified URL ’http://localhost.example’. • $response will contain the response body after the call to the file_get_contents function completes. • $http_response_header is implicitly populated with the HTTP response status line and headers after the file_get_contents call because it uses the HTTP streams wrapper within the current scope. While this example does work, it violates a core principle of good coding practices: no unexpected side effects. The origin of $http_response_header is not entirely ob vious because PHP populates it implicitly. Additionally, it’s more restrictive because the variable is only populated within the scope containing the call to file_get_contents. H ere’s a better way to get access to the same data from the response headers.
HTTP Streams W rapper ” 29 Let’s step through this. • The resource $handle is created to read from the URL http://localhost.example. • The stream_get_contents function is called to read the remaining data on the stream pointed to by the $handle resource into $response. • The stream_get_meta_data function is called to read metadata for the stream pointed to by the $handle resource into $meta. • The wrapper_data index of the $meta array outputs the same array as $http_response_header would within the current scope. So long as $handle is accessible within the current scope, stream_get_meta_data() can be called on it. This makes it more flexible than $http_response_header. S tr eam Contexts and POST Requests Another concept introduced by streams is the context, which is basically a set of configuration options used in a streams operation. A context is created by passing an associative array of context options and their corresponding values to the stream_context_create function. One use of contexts with regard to the HTTP streams wrapper is making POST requests, as the wrapper uses the GET method by default.
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A p p e n d i x A Legality of W e S
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