<?php

if (getenv('REQUEST_METHOD') == 'POST') {
  $url = $_POST[url];
} else {
  $url = $_GET[url];
}
?>

<form action="<?= $PHP_SELF ?>" method="POST">
URL:<input type="text" name="url" value="<?= $url ?>"/><br>
<input type="submit">
</form>

<?php
  if ($url) {
    $remote = fopen($url, 'r');
    $html = fread($remote, 1048576); // read up to 1 MB of HTML
    fclose($remote);

    $urls = '(http|telnet|gopher|file|wais|ftp)';
    $ltrs = '\w';
    $gunk = '/#~:.?+=&%@!\-';
    $punc = '.:?\-';
    $any = "$ltrs$gunk$punc";
    preg_match_all("{
                      \b          # start at word boundary
                      $urls   :   # need resource and a colon
                      [$any] +?   # followed by one or more of any valid
                                  #   characters--but be conservative
                                  #   and take only what you need
                      (?=         # the match ends at
                        [$punc] * # punctuation
                        [^$any]   # followed by a non-URL character
                      |           # or
                        $         # the end of the string
                      )
                  }x", $html, $matches);
    printf("I found %d URLs<P>\n", sizeof($matches[0]));
    foreach ($matches[0] as $u) {
      $link = $PHP_SELF . '?url=' . urlencode($u);
      echo "<A HREF='$link'>$u</A><BR>\n";
    }
  }
?>