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<h1 class="title">Introduction</h1>
<p class="simpara">
Streams were introduced with PHP 4.3.0 as
a way of generalizing file, network, data compression, and other
operations which share a common set of functions and uses. In
its simplest definition, a <em>stream</em> is a
<em>resource</em> object which exhibits streamable
behavior. That is, it can be read from or written to in a linear
fashion, and may be able to <span class="function"><a href="function.fseek.html" class="function">fseek()</a></span> to an
arbitrary locations within the stream.
</p>
<p class="simpara">
A <em>wrapper</em> is additional code which tells the stream how to handle
specific protocols/encodings. For example, the <em>http</em>
wrapper knows how to translate a URL into an <em>HTTP/1.0</em>
request for a file on a remote server. There are many wrappers
built into PHP by default (See <a href="wrappers.html" class="xref">Supported Protocols and Wrappers</a>),
and additional, custom wrappers may be added either within a
PHP script using <span class="function"><a href="function.stream-wrapper-register.html" class="function">stream_wrapper_register()</a></span>,
or directly from an extension using the API Reference in <a href="internals2.streams.html" class="xref">Working with streams</a>.
Because any variety of wrapper may be added to PHP,
there is no set limit on what can be done with them. To access the list
of currently registered wrappers, use <span class="function"><a href="function.stream-get-wrappers.html" class="function">stream_get_wrappers()</a></span>.
</p>
<p class="para">
A stream is referenced as: <em><code class="parameter">scheme</code></em>://<em><code class="parameter">target</code></em>
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara">
<em><code class="parameter">scheme</code></em>(string) -
The name of the wrapper to be used. Examples include: file,
http, https, ftp, ftps, compress.zlib, compress.bz2, and php. See
<a href="wrappers.html" class="xref">Supported Protocols and Wrappers</a> for a list of PHP built-in wrappers. If
no wrapper is specified, the function default is used (typically
<em>file</em>://).
</span>
</li>
<li class="listitem">
<span class="simpara">
<em><code class="parameter">target</code></em> -
Depends on the wrapper used. For filesystem related streams this is
typically a path and filename of the desired file. For network related
streams this is typically a hostname, often with a path appended. Again, see
<a href="wrappers.html" class="xref">Supported Protocols and Wrappers</a> for a description of targets for built-in streams.
</span>
</li>
</ul>
</p>
<p class="para">
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Information on using streams within the PHP source code can be found in the
<a href="internals2.ze1.streams.html" class="link">Streams API for PHP Extension Authors reference</a>.
</p>
</p></blockquote>
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