<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Attach a filter to a stream</title>
</head>
<body><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.stream-encoding.html">stream_encoding</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.stream-filter-prepend.html">stream_filter_prepend</a></div>
<div class="up"><a href="ref.stream.html">Stream Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="function.stream-filter-append" class="refentry">
<div class="refnamediv">
<h1 class="refname">stream_filter_append</h1>
<p class="verinfo">(PHP 4 >= 4.3.0, PHP 5)</p><p class="refpurpose"><span class="refname">stream_filter_append</span> — <span class="dc-title">Attach a filter to a stream</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.stream-filter-append-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">resource</span> <span class="methodname"><strong>stream_filter_append</strong></span>
( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$stream</code></span>
, <span class="methodparam"><span class="type">string</span> <code class="parameter">$filtername</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$read_write</code></span>
[, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$params</code></span>
]] )</div>
<p class="para rdfs-comment">
Adds <em><code class="parameter">filtername</code></em> to the list of filters
attached to <em><code class="parameter">stream</code></em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.stream-filter-append-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">stream</code></em></span>
<dd>
<p class="para">
The target stream.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">filtername</code></em></span>
<dd>
<p class="para">
The filter name.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">read_write</code></em></span>
<dd>
<p class="para">
By default, <span class="function"><strong>stream_filter_append()</strong></span> will
attach the filter to the <em>read filter chain</em>
if the file was opened for reading (i.e. File Mode:
<em>r</em>, and/or <em>+</em>). The filter
will also be attached to the <em>write filter chain</em>
if the file was opened for writing (i.e. File Mode:
<em>w</em>, <em>a</em>, and/or <em>+</em>).
<strong><code>STREAM_FILTER_READ</code></strong>,
<strong><code>STREAM_FILTER_WRITE</code></strong>, and/or
<strong><code>STREAM_FILTER_ALL</code></strong> can also be passed to the
<em><code class="parameter">read_write</code></em> parameter to override this behavior.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">params</code></em></span>
<dd>
<p class="para">
This filter will be added with the specified
<em><code class="parameter">params</code></em> to the <em class="emphasis">end</em> of
the list and will therefore be called last during stream operations.
To add a filter to the beginning of the list, use
<span class="function"><a href="function.stream-filter-prepend.html" class="function">stream_filter_prepend()</a></span>.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.stream-filter-append-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns a resource which can be used to refer to this filter
instance during a call to <span class="function"><a href="function.stream-filter-remove.html" class="function">stream_filter_remove()</a></span>.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.stream-filter-append-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>5.1.0</td>
<td>
Prior to PHP 5.1.0, this function returns <strong><code>TRUE</code></strong> on success
or <strong><code>FALSE</code></strong> on failure.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.stream-filter-append-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4016">
<p><strong>Example #1 Controlling where filters are applied</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/* Open a test file for reading and writing */<br /></span><span style="color: #0000BB">$fp </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'test.txt'</span><span style="color: #007700">, </span><span style="color: #DD0000">'w+'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Apply the ROT13 filter to the<br /> * write filter chain, but not the<br /> * read filter chain */<br /></span><span style="color: #0000BB">stream_filter_append</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #DD0000">"string.rot13"</span><span style="color: #007700">, </span><span style="color: #0000BB">STREAM_FILTER_WRITE</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Write a simple string to the file<br /> * it will be ROT13 transformed on the<br /> * way out */<br /></span><span style="color: #0000BB">fwrite</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #DD0000">"This is a test\n"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Back up to the beginning of the file */<br /></span><span style="color: #0000BB">rewind</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Read the contents of the file back out.<br /> * Had the filter been applied to the<br /> * read filter chain as well, we would see<br /> * the text ROT13ed back to its original state */<br /></span><span style="color: #0000BB">fpassthru</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">fclose</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Expected Output<br /> ---------------<br /><br />Guvf vf n grfg<br /><br /> */<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.stream-filter-append-notes">
<h3 class="title">Notes</h3>
<blockquote class="note"><p><strong class="note">Note</strong>:
<strong>When using custom (user) filters</strong><br />
<span class="simpara">
<span class="function"><a href="function.stream-filter-register.html" class="function">stream_filter_register()</a></span> must be called first
in order to register the desired user filter to <em><code class="parameter">filtername</code></em>.
</span>
</p></blockquote>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
Stream data is read from resources (both local and remote) in chunks,
with any unconsumed data kept in internal buffers. When a new
filter is appended to a stream, data in the internal buffers is processed through
the new filter at that time. This differs from the behavior of
<span class="function"><a href="function.stream-filter-prepend.html" class="function">stream_filter_prepend()</a></span>.
</span>
</p></blockquote>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
When a filter is added for read and write, two instances of the filter
are created. <span class="function"><strong>stream_filter_append()</strong></span> must be called twice
with <strong><code>STREAM_FILTER_READ</code></strong> and
<strong><code>STREAM_FILTER_WRITE</code></strong> to get both filter resources.
</span>
</p></blockquote>
</div>
<div class="refsect1 seealso" id="refsect1-function.stream-filter-append-seealso">
<h3 class="title">See Also</h3>
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.stream-filter-register.html" class="function" rel="rdfs-seeAlso">stream_filter_register()</a> - Register a user defined stream filter</span></li>
<li class="member"> <span class="function"><a href="function.stream-filter-prepend.html" class="function" rel="rdfs-seeAlso">stream_filter_prepend()</a> - Attach a filter to a stream</span></li>
<li class="member"> <span class="function"><a href="function.stream-get-filters.html" class="function" rel="rdfs-seeAlso">stream_get_filters()</a> - Retrieve list of registered filters</span></li>
</ul>
</div>
</div><hr /><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.stream-encoding.html">stream_encoding</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.stream-filter-prepend.html">stream_filter_prepend</a></div>
<div class="up"><a href="ref.stream.html">Stream Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
