PHP Script Version Checking/Notification

define('REMOTE_VERSION', 'http://your.public.server/version.txt');

// this is the version of the deployed script
define('VERSION', '1.0.1');

function isUpToDate()
{
    $remoteVersion=trim(file_get_contents(REMOTE_VERSION));
    return version_compare(VERSION, $remoteVersion, 'ge');
}

1.0.2

// Substitue path to script with the version information in place of __FILE__ if necessary
$script = file_get_contents(__FILE__);
$version = SOME_SENSIBLE_DEFAULT_IN_CASE_OF_FAILURE;
if(preg_match('/<!-- Script version (d*(.d+)*) -->/', $script, $version_match)) {
    $version = $version_match[1];
}

define('REMOTE_VERSION', 'http://your.public.server/version.txt');
define('VERSION', '1.0.1');
$script = file_get_contents(REMOTE_VERSION);
$version = VERSION;
if($version == $script) {
    echo "<div class=success>
<p>You have the latest version!</p>
</div>";
} else {
    echo "<div class=error>
<p>There is a update available!</p>
</div>";
}