The following is a function to redirect to a new URL. It will use either a header() call or output javascript, a meta refresh, and a link depending on whether output has been started. It will also intelligently fix your URL to make it absolute (the Location header technically requires an absolute URL).

function redirect($url = false) {
    if (empty($url) || substr($url, 0, 4) !== 'http') {
        $url = 'http'.(isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off' ? 's' : '').'://'.$_SERVER['HTTP_HOST'].
            (!empty($url) && $url[0] == '/'
             ? ''                                      //if the URL is already from the root
             : (empty($url) || $url[0] == '?'
                ? $_SERVER['PHP_SELF']                 //if the url is empty or starts with ?, prefix with current dir & script
                : dirname($_SERVER['PHP_SELF']).'/')). //if the url is not empty and does not start with ?, add current dir
            $url;
    }
    if ((stristr($_SERVER['HTTP_USER_AGENT'], 'MSIE') && stristr($_SERVER['HTTP_USER_AGENT'], 'Mac')) || headers_sent()) {
          echo '<script language="JavaScript1.1">
<!--
location.replace("'.$url.'");
//-->
</script>
<noscript>
<meta http-equiv="Refresh" content="0; URL='.htmlentities($url, ENT_QUOTES).'"/>
</noscript>
Please <a href="'.htmlentities($url, ENT_QUOTES).'">click here</a> to continue.
';
    } else {
        header('Location: '.$url);
        header('Connection: close');
    }
    exit;
}

There are also a few other peculiarities above. First off the header() call is never used for IE:mac. It doesn't handle header redirects well. (Of course this browser is very old and unmaintained, but I included it for completeness.) The Connection: close is also sent when header() is used to stop IE from trying to use keep-alive when it is redirected from http to https or vice-versa.

/**
 * does a regular split, but also accounts for the deliminator to be within quoted fields
 *  for example, if called as such:
 *   splitQuoteFriendly(',', '0,1,2,"3,I am still 3",4');
 *  it will return:
 *   array(0 => '0',
 *         1 => '1',
 *         2 => '2',
 *         3 => '"3,I am still 3"',
 *         4 => '4');
 * @param string deliminator to split by
 * @param string text to split
 * @param string text which surrounds quoted fields (defaults to ")
 * @return array array of fields after split
 */
function splitQuoteFriendly($delim, $text, $quote = '"') {
    $strictFields = explode($delim, $text);
    for($sl = 0, $l = 0; $sl < sizeof($strictFields); ++$sl) {
        $fields[$l] = $strictFields[$sl];
        $numQuotes = 0;
        while(fmod($numQuotes += substr_count($strictFields[$sl], $quote), 2) == 1) {
            ++$sl;
            $fields[$l] .= $delim.$strictFields[$sl];
        }
        ++$l;
    }
 
    return $fields;
}