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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<chapter xml:id="features.remote-files" xmlns="http://docbook.org/ns/docbook">
<title>Using remote files</title>
<para>
As long as <option>allow_url_fopen</option> is enabled in
&php.ini;, you can use <acronym>HTTP</acronym> and <acronym>FTP</acronym>
URLs with most of the functions
that take a filename as a parameter. In addition, URLs can be
used with the <function>include</function>,
<function>include_once</function>, <function>require</function> and
<function>require_once</function> statements (since PHP 5.2.0,
<option>allow_url_include</option> must be enabled for these).
See <xref linkend="wrappers"/> for more information about the protocols
supported by PHP.
</para>
<note>
<para>
In PHP 4.0.3 and older, in order to use URL wrappers, you were required
to configure PHP using the configure option
<option>--enable-url-fopen-wrapper</option>.
</para>
</note>
<para>
<note>
<para>
The Windows versions of PHP earlier than PHP 4.3
did not support remote file accessing for the following functions:
<function>include</function>, <function>include_once</function>,
<function>require</function>, <function>require_once</function>,
and the imagecreatefromXXX functions in the <xref linkend="ref.image"/>
extension.
</para>
</note>
</para>
<para>
For example, you can use this to open a file on a remote web server,
parse the output for the data you want, and then use that data in a
database query, or simply to output it in a style matching the rest
of your website.
</para>
<para>
<example>
<title>Getting the title of a remote page</title>
<programlisting role="php">
<![CDATA[
<?php
$file = fopen ("http://www.example.com/", "r");
if (!$file) {
echo "<p>Unable to open remote file.\n";
exit;
}
while (!feof ($file)) {
$line = fgets ($file, 1024);
/* This only works if the title and its tags are on one line */
if (preg_match ("@\<title\>(.*)\</title\>@i", $line, $out)) {
$title = $out[1];
break;
}
}
fclose($file);
?>
]]>
</programlisting>
</example>
</para>
<para>
You can also write to files on an FTP server (provided that you
have connected as a user with the correct access rights). You
can only create new files using this method; if you try to overwrite
a file that already exists, the <function>fopen</function> call will
fail.
</para>
<para>
To connect as a user other than 'anonymous', you need to specify
the username (and possibly password) within the URL, such as
'<literal>ftp://user:password@ftp.example.com/path/to/file</literal>'.
(You can use the same sort of syntax to access files via
<acronym>HTTP</acronym> when they require Basic authentication.)
</para>
<para>
<example>
<title>Storing data on a remote server</title>
<programlisting role="php">
<![CDATA[
<?php
$file = fopen ("ftp://ftp.example.com/incoming/outputfile", "w");
if (!$file) {
echo "<p>Unable to open remote file for writing.\n";
exit;
}
/* Write the data here. */
fwrite ($file, $_SERVER['HTTP_USER_AGENT'] . "\n");
fclose ($file);
?>
]]>
</programlisting>
</example>
</para>
<para>
<note>
<para>
You might get the idea from the example above that you can use
this technique to write to a remote log file. Unfortunately
that would not work because the <function>fopen</function> call will
fail if the remote file already exists. To do distributed logging
like that, you should take a look at <function>syslog</function>.
</para>
</note>
</para>
</chapter>
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