PHP: Dynamic URL Question.

Question

Hi, The variable ' $return10 ' (for example) is a url, and I need to append ' &var2=example ' to the end. Like this:

 header( "Location: $return10&var2=example" );
 header ("Content-Length: 0");
  exit;

The challenge is not knowing if the url contained in ' $return10 ' will already have a query string.

Choice A) If I use ' &var2=example ' , then sometimes the final url will be ' ://example.com&var2=example ' , with no '?' to start the query string.

Choice B) If I use ' ?var2=example ' , then sometimes the final url will contain two "?"'s starting two different query strings??

Is there a third choice? How would you cover both possibilities using "the correct code?" Thank you.

Answer 1

You can construct the URI seperately:

if(!strpos($uri, "?"))
  $uri .= "&var2=example"
else
  $uri .= "?var2=example"

header("Location: $uri");

Answer 2

Create a function that will append your query code if there is one... And add it if there isn't...

function append_query($url, $query) {
  // Fix for relative scheme URL
  $relativeScheme = false;
  if(substr($url, 0, 3) == '://') {
    $relativeScheme = true;
    $url = 'a' . $url;
  }

  $newUrl = http_build_url($url, array('query' => $query), HTTP_URL_JOIN_QUERY);

  if($relativeScheme) {
    return substr($newUrl, 1);
  }

  return $newUrl;
}

header('Location: ' . append_query($return10, 'var2=example'));

This will work regardless of if your query has a fragment or not.

EDIT: Fixed for relative scheme URL.

If your PHP does not have http_build_url() available (ie.: PECL extension not installed), here is a pure PHP version of it which does not require the extension.

define('HTTP_URL_REPLACE', 1);          // Replace every part of the first URL when there's one of the second URL
define('HTTP_URL_JOIN_PATH', 2);        // Join relative paths
define('HTTP_URL_JOIN_QUERY', 4);       // Join query strings
define('HTTP_URL_STRIP_USER', 8);       // Strip any user authentication information
define('HTTP_URL_STRIP_PASS', 16);      // Strip any password authentication information
define('HTTP_URL_STRIP_AUTH', 32);      // Strip any authentication information
define('HTTP_URL_STRIP_PORT', 64);      // Strip explicit port numbers
define('HTTP_URL_STRIP_PATH', 128);     // Strip complete path
define('HTTP_URL_STRIP_QUERY', 256);    // Strip query string
define('HTTP_URL_STRIP_FRAGMENT', 512); // Strip any fragments (#identifier)
define('HTTP_URL_STRIP_ALL', 1024);     // Strip anything but scheme and host

// Build an URL
// The parts of the second URL will be merged into the first according to the flags argument.
//
// @param mixed     (Part(s) of) an URL in form of a string or associative array like parse_url() returns
// @param mixed     Same as the first argument
// @param int       A bitmask of binary or'ed HTTP_URL constants (Optional)HTTP_URL_REPLACE is the default
// @param array     If set, it will be filled with the parts of the composed url like parse_url() would return
function http_build_url($url, $parts = array (), $flags = HTTP_URL_REPLACE, &$new_url = false) {
  $keys = array (
    'user',
    'pass',
    'port',
    'path',
    'query',
    'fragment'
  );

  // HTTP_URL_STRIP_ALL becomes all the HTTP_URL_STRIP_Xs
  if ($flags & HTTP_URL_STRIP_ALL) {
    $flags |= HTTP_URL_STRIP_USER;
    $flags |= HTTP_URL_STRIP_PASS;
    $flags |= HTTP_URL_STRIP_PORT;
    $flags |= HTTP_URL_STRIP_PATH;
    $flags |= HTTP_URL_STRIP_QUERY;
    $flags |= HTTP_URL_STRIP_FRAGMENT;
  }
  // HTTP_URL_STRIP_AUTH becomes HTTP_URL_STRIP_USER and HTTP_URL_STRIP_PASS
  else if ($flags & HTTP_URL_STRIP_AUTH) {
    $flags |= HTTP_URL_STRIP_USER;
    $flags |= HTTP_URL_STRIP_PASS;
  }

  // Parse the original URL
  $parse_url = parse_url($url);

  // Scheme and Host are always replaced
  if (isset($parts['scheme']))
    $parse_url['scheme'] = $parts['scheme'];

  if (isset($parts['host']))
    $parse_url['host'] = $parts['host'];

  // (If applicable) Replace the original URL with it's new parts
  if ($flags & HTTP_URL_REPLACE) {
    foreach ($keys as $key) {
      if (isset($parts[$key]))
        $parse_url[$key] = $parts[$key];
    }
  } else {
    // Join the original URL path with the new path
    if (isset($parts['path']) && ($flags & HTTP_URL_JOIN_PATH)) {
      if (isset($parse_url['path']))
        $parse_url['path'] = rtrim(str_replace(basename($parse_url['path']), '', $parse_url['path']), '/') . '/' . ltrim($parts['path'], '/');
      else
        $parse_url['path'] = $parts['path'];
    }

    // Join the original query string with the new query string
    if (isset($parts['query']) && ($flags & HTTP_URL_JOIN_QUERY)) {
      if (isset($parse_url['query']))
        $parse_url['query'] .= '&' . $parts['query'];
      else
        $parse_url['query'] = $parts['query'];
    }
  }

  // Strips all the applicable sections of the URL
  // Note: Scheme and Host are never stripped
  foreach ($keys as $key) {
    if ($flags & (int)constant('HTTP_URL_STRIP_' . strtoupper($key)))
      unset($parse_url[$key]);
  }

  $new_url = $parse_url;

  return ((isset($parse_url['scheme'])) ? $parse_url['scheme'] . '://' : '') . ((isset($parse_url['user'])) ? $parse_url['user'] . ((isset($parse_url['pass'])) ? ':' . $parse_url['pass'] : '') . '@' : '')
    . ((isset($parse_url['host'])) ? $parse_url['host'] : '') . ((isset($parse_url['port'])) ? ':' . $parse_url['port'] : '') . ((isset($parse_url['path'])) ? $parse_url['path'] : '')
    . ((isset($parse_url['query'])) ? '?' . $parse_url['query'] : '') . ((isset($parse_url['fragment'])) ? '#' . $parse_url['fragment'] : '');
}

Answer 3

Take a look at http://php.net/manual/en/function.parse-url.php and http://www.php.net/manual/en/function.http-build-url.php.

Now you can do something like this:

<?php
$return10 = '... some url here ...';
$newUrl = http_build_url(
    $return10,
    array('query' => 'var2=example'),
    HTTP_URL_JOIN_QUERY
);
?>