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<title>Runtime Configuration</title>
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<h2 class="title">Runtime Configuration</h2>
<p class="simpara">
The behaviour of these functions is affected by settings in <var class="filename">php.ini</var>.
</p>
<p class="para">
<table class="doctable table">
<caption><strong>Output Control configuration options</strong></caption>
<thead>
<tr>
<th>Name</th>
<th>Default</th>
<th>Changeable</th>
<th>Changelog</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td><a href="outcontrol.configuration.html#ini.output-buffering" class="link">output_buffering</a></td>
<td>"0"</td>
<td>PHP_INI_PERDIR</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="outcontrol.configuration.html#ini.output-handler" class="link">output_handler</a></td>
<td>NULL</td>
<td>PHP_INI_PERDIR</td>
<td>Available since PHP 4.0.4.</td>
</tr>
<tr>
<td><a href="outcontrol.configuration.html#ini.implicit-flush" class="link">implicit_flush</a></td>
<td>"0"</td>
<td>PHP_INI_ALL</td>
<td>PHP_INI_PERDIR in PHP <= 4.2.3.</td>
</tr>
<tr>
<td><a href="outcontrol.configuration.html#ini.url-rewriter.tags" class="link">url_rewriter.tags</a></td>
<td>"a=href,area=href,frame=src,form=,fieldset="</td>
<td>PHP_INI_ALL</td>
<td>Available since PHP 4.0.4. Before PHP 7.1.0, this was used to set
session's trans sid rewrite. From PHP 7.1.0, it is only used by
<span class="function"><a href="function.output-add-rewrite-var.html" class="function">output_add_rewrite_var()</a></span>.</td>
</tr>
<tr>
<td><a href="outcontrol.configuration.html#ini.url-rewriter.hosts" class="link">url_rewriter.hosts</a></td>
<td><em>$_SERVER['HTTP_HOST']</em> is used as default.</td>
<td>PHP_INI_ALL</td>
<td>Available since PHP 7.1.0</td>
</tr>
</tbody>
</table>
For further details and definitions of the
PHP_INI_* modes, see the <a href="configuration.changes.modes.html" class="xref">Where a configuration setting may be set</a>.
</p>
<p class="para">Here's a short explanation of
the configuration directives.</p>
<p class="para">
<dl>
<dt id="ini.output-buffering">
<code class="parameter">output_buffering</code>
<span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>/<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
You can enable output buffering for all files by setting this directive
to 'On'. If you wish to limit the size of the buffer to a certain size -
you can use a maximum number of bytes instead of 'On', as a value for
this directive (e.g., output_buffering=4096).
This directive is always Off in PHP-CLI.
</p>
</dd>
<dt id="ini.output-handler">
<code class="parameter">output_handler</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
You can redirect all of the output of your scripts to a function. For
example, if you set output_handler to
<span class="function"><a href="function.mb-output-handler.html" class="function">mb_output_handler()</a></span>, character encoding will be
transparently converted to the specified encoding. Setting any output
handler automatically turns on output buffering.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
You cannot use both <span class="function"><a href="function.mb-output-handler.html" class="function">mb_output_handler()</a></span> with
<span class="function"><a href="function.ob-iconv-handler.html" class="function">ob_iconv_handler()</a></span> and you cannot use both
<span class="function"><a href="function.ob-gzhandler.html" class="function">ob_gzhandler()</a></span> and
<a href="zlib.configuration.html#ini.zlib.output-compression" class="link">zlib.output_compression</a>.
</p>
</p></blockquote>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Only built-in functions can be used with this directive. For user
defined functions, use <span class="function"><a href="function.ob-start.html" class="function">ob_start()</a></span>.
</p>
</p></blockquote>
</dd>
<dt id="ini.implicit-flush">
<code class="parameter">implicit_flush</code>
<span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>
</dt>
<dd>
<p class="para">
<strong><code>FALSE</code></strong> by default. Changing this to <strong><code>TRUE</code></strong> tells PHP to tell the
output layer to flush itself automatically after every output block.
This is equivalent to calling the PHP function
<span class="function"><a href="function.flush.html" class="function">flush()</a></span> after each and every call to
<span class="function"><a href="function.print.html" class="function">print</a></span> or <span class="function"><a href="function.echo.html" class="function">echo</a></span> and each and
every <em>HTML</em> block.
</p>
<p class="para">
When using PHP within an web environment, turning
this option on has serious performance implications and is generally
recommended for debugging purposes only. This value defaults to
<strong><code>TRUE</code></strong> when operating under the <em>CLI SAPI</em>.
</p>
<p class="para">
See also <span class="function"><a href="function.ob-implicit-flush.html" class="function">ob_implicit_flush()</a></span>.
</p>
</dd>
<dt id="ini.url-rewriter.tags">
<code class="parameter">url_rewriter.tags</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<span class="simpara">
<em>url_rewriter.tags</em> specifies which HTML tags
are rewritten by <span class="function"><a href="function.output-add-rewrite-var.html" class="function">output_add_rewrite_var()</a></span> values.
Defaults to
<em>a=href,area=href,frame=src,input=src,form=</em>
</span>
<span class="simpara">
<em>form</em> is special tag. <em><input hidden="session_id" name="session_name"></em>
is added as form variable.
</span>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
Before PHP 7.1.0, <a href="outcontrol.configuration.html#ini.url-rewriter.tags" class="link">url_rewriter.tags</a>
was used to specify <a href="session.configuration.html#ini.session.trans-sid-tags" class="link">session.trans_sid_tags</a>.
Since PHP 7.1.0, <em>fieldset</em> is no longer considered as special tag.
</span>
</p></blockquote>
</dd>
<dt id="ini.url-rewriter.hosts">
<code class="parameter">url_rewriter.hosts</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<span class="simpara">
<em>url_rewriter.hosts</em> specifies which hosts are
rewritten to include <span class="function"><a href="function.output-add-rewrite-var.html" class="function">output_add_rewrite_var()</a></span> values.
Defaults to <em>$_SERVER['HTTP_HOST']</em>. Multiple hosts
can be specified by ",", no space is allowed between hosts. e.g.
<em>php.net,wiki.php.net,bugs.php.net</em>
</span>
</dd>
</dl>
</p>
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