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<div class="refnamediv">
<h1 class="refname">header_register_callback</h1>
<p class="verinfo">(No version information available, might only be in SVN)</p><p class="refpurpose"><span class="refname">header_register_callback</span> — <span class="dc-title">Call a header function</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.header-register-callback-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><strong>header_register_callback</strong></span>
( <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
)</div>
<p class="para rdfs-comment">
Registers a function that will be called when PHP starts sending output.
</p>
<p class="para">
The <em><code class="parameter">callback</code></em> is executed just after PHP prepares all
headers to be sent, and before any other output is sent, creating a window
to manipulate the outgoing headers before being sent.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.header-register-callback-parameters">
<h3 class="title">Parameters</h3>
<dl>
<dt>
<span class="term"><em><code class="parameter">callback</code></em></span>
<dd>
<p class="para">
Function called just before the headers are sent. It gets no parameters
and the return value is ignored.
</p>
</dd>
</dt>
</dl>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.header-register-callback-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns <strong><code>TRUE</code></strong> on success or <strong><code>FALSE</code></strong> on failure.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.header-register-callback-examples">
<h3 class="title">Examples</h3>
<div class="example" id="header-register-callback.example.basic">
<p><strong>Example #1 <span class="function"><strong>header_register_callback()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />header</span><span style="color: #007700">(</span><span style="color: #DD0000">'Content-Type: text/plain'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">header</span><span style="color: #007700">(</span><span style="color: #DD0000">'X-Test: foo'</span><span style="color: #007700">);<br /><br />function </span><span style="color: #0000BB">foo</span><span style="color: #007700">() {<br /> foreach (</span><span style="color: #0000BB">headers_list</span><span style="color: #007700">() as </span><span style="color: #0000BB">$header</span><span style="color: #007700">) {<br /> if (</span><span style="color: #0000BB">strpos</span><span style="color: #007700">(</span><span style="color: #0000BB">$header</span><span style="color: #007700">, </span><span style="color: #DD0000">'X-Powered-By:'</span><span style="color: #007700">) !== </span><span style="color: #0000BB">false</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">header_remove</span><span style="color: #007700">(</span><span style="color: #DD0000">'X-Powered-By'</span><span style="color: #007700">);<br /> }<br /> </span><span style="color: #0000BB">header_remove</span><span style="color: #007700">(</span><span style="color: #DD0000">'X-Test'</span><span style="color: #007700">);<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$result </span><span style="color: #007700">= </span><span style="color: #0000BB">header_register_callback</span><span style="color: #007700">(</span><span style="color: #DD0000">'foo'</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">"a"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Content-Type: text/plain
a
</pre></div>
</div>
</div>
</div>
<div class="refsect1 notes" id="refsect1-function.header-register-callback-notes">
<h3 class="title">Notes</h3>
<p class="para">
<span class="function"><strong>header_register_callback()</strong></span> is executed just as the
headers are about to be sent out, so any output from this function can
break output.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Headers will only be accessible and output when a SAPI that supports them
is in use.
</p>
</p></blockquote>
</div>
<div class="refsect1 seealso" id="refsect1-function.header-register-callback-seealso">
<h3 class="title">See Also</h3>
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.headers-list.html" class="function" rel="rdfs-seeAlso">headers_list()</a> - Returns a list of response headers sent (or ready to send)</span></li>
<li class="member"> <span class="function"><a href="function.header-remove.html" class="function" rel="rdfs-seeAlso">header_remove()</a> - Remove previously set headers</span></li>
<li class="member"> <span class="function"><a href="function.header.html" class="function" rel="rdfs-seeAlso">header()</a> - Send a raw HTTP header</span></li>
</ul>
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