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><A
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>Capítulo 44. Streams API for PHP Extension Authors</A
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><DT
><B
>Índice</B
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><A
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>Overview</A
></DT
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>Streams Basics</A
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>Streams as Resources</A
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>Streams Common API Reference</A
></DT
><DT
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>Streams Dir API Reference</A
></DT
><DT
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>Streams File API Reference</A
></DT
><DT
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>Streams Socket API Reference</A
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>Streams Structures</A
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>Streams Constants</A
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>Overview</A
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><P
> The PHP Streams API introduces a unified approach to the handling of
files and sockets in PHP extension. Using a single API with standard
functions for common operations, the streams API allows your extension
to access files, sockets, URLs, memory and script-defined objects.
Streams is a run-time extensible API that allows dynamically loaded
modules (and scripts!) to register new streams.
</P
><P
> The aim of the Streams API is to make it comfortable for developers to
open files, URLs and other streamable data sources with a unified API
that is easy to understand. The API is more or less based on the ANSI
C stdio family of functions (with identical semantics for most of the main
functions), so C programmers will have a feeling of familiarity with streams.
</P
><P
> The streams API operates on a couple of different levels: at the base level,
the API defines php_stream objects to represent streamable data sources.
On a slightly higher level, the API defines php_stream_wrapper objects
which "wrap" around the lower level API to provide support for retrieving
data and meta-data from URLs. An additional <TT
CLASS="literal"
>context</TT
>
parameter, accepted by most stream creation functions, is passed to the
wrapper's <TT
CLASS="literal"
>stream_opener</TT
> method to fine-tune the behavior
of the wrapper.
</P
><P
> Any stream, once opened, can also have any number of <TT
CLASS="literal"
>filters</TT
>
applied to it, which process data as it is read from/written to the stream.
</P
><P
> Streams can be cast (converted) into other types of file-handles, so that they
can be used with third-party libraries without a great deal of trouble. This
allows those libraries to access data directly from URL sources. If your
system has the <B
CLASS="function"
>fopencookie()</B
> or
<B
CLASS="function"
>funopen()</B
> function, you can even
pass any PHP stream to any library that uses ANSI stdio!
</P
><P
> <DIV
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><BLOCKQUOTE
CLASS="note"
><P
><B
>Nota: </B
>
The functions in this chapter are for use in the PHP source code and
are not PHP functions. Userland stream functions can be found in the
<A
HREF="ref.stream.html"
>Stream Reference</A
>.
</P
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