Ubuntu PHP href链接不起作用

I have PHP Version 7.0.8-0ubuntu0.16.04.3 running on a server at home.

I am trying to link to a file using;

<?php echo "Software Version - " . $thisVersion. "<a href=\"includes/getUpdate.php\">" . $updateAvalable . "</a>"; ?>

The text in the $updateAvailable string gets displayed as a link but does nothing when clicked on.

What is perplexing is that this same piece of code works fine on a remote server I have access to. I suspect this maybe due to some setting on my home server but I am at a loss with this now.

Cheers in advance for any help.

Here most off the code;

$serverVersion = "ftp://ServerLogonDetails/someText.txt";
$handle = fopen($serverVersion, "r");
$latestVersion = fgets($handle);
fclose;

// Get the software version 
if (($_SESSION[Page] == "Config")||($_SESSION[Page] == "backUpRec")){
    $localVersion = "daemon_ver.txt";
    $handle = fopen($localVersion, "r") or die($openLocalFile = FALSE);
    $currentVersion = fgets($handle);
    fclose;
}
else if (($_SESSION[Page] == "System")||($_SESSION[Page] == "Users")){
    // Get the software version on the VS-One unit
    $localVersion = "../daemon_ver.txt";
    $handle = fopen($localVersion, "r") or die($openLocalFile = TRUE);
    $currentVersion = fgets($handle);
    fclose;
}

if ($latestVersion <= $currentVersion) {
    $updateAvalable = "";
}
else if ($latestVersion > $currentVersion){
    $updateAvalable = " Update Available";
}

?>

</head>
<body>

<table id="footersmall" width="940" border="0" cellspacing="10" cellpadding="0">
    <tr>
        <td class="version"><?php echo "Software Version - ".$thisVersion."<a href=\"includes/getUpdate.php\">".$updateAvalable . "</a>"; ?></td>
    </tr>
</table>
</body>
</html>

try slash at beginning "<a href=\"/includes/getUpdate.php\">"

...if "includes" is at the web root, of cause...