Chapter 19. Using remote files

As long as allow_url_fopen is enabled in php.ini, you can use HTTP and FTP URLs with most of the functions that take a filename as a parameter. In addition, URLs can be used with the include(), include_once(), require() and require_once() statements. See Appendix J for more information about the protocols supported by PHP.

Note: In PHP 4.0.3 and older, in order to use URL wrappers, you were required to configure PHP using the configure option --enable-url-fopen-wrapper.

Note: The Windows versions of PHP earlier than PHP 4.3 did not support remote file accessing for the following functions: include(), include_once(), require(), require_once(), and the imagecreatefromXXX functions in the Reference XLI, Image Functions extension.

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.

Example 19-1. Getting the title of a remote page

 <?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 (eregi ("<title>(.*)</title>", $line, $out)) {
        $title = $out[1];
        break;
    }
}
fclose($file);
?>

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 fopen() call will fail.

To connect as a user other than 'anonymous', you need to specify the username (and possibly password) within the URL, such as 'ftp://user:password@ftp.example.com/path/to/file'. (You can use the same sort of syntax to access files via HTTP when they require Basic authentication.)

Example 19-2. Storing data on a remote server

 <?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);
?>

Note: 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 fopen() call will fail if the remote file already exists. To do distributed logging like that, you should take a look at syslog().