Add custom text to the end of .date

Question

I have a small section of code in my site showing when the index.php was last modified, it looks like this:

<?php
    $filename = 'index.php';
    if (file_exists($filename)) {
        echo "<p style=text-align:center'>$filename was last modified: " .date ("F d Y G:i P ",   filemtime($filename));
    }
php?>

It currently displays as, index.php was last modified: December 30 2013 12:36 +01:00

But where the +01:00 is at the end, I would like to add the text 'GMT' so user can know it's +1 GMT.

Struggling to work out how to get it in there without breaking the code.

Answer 1

echo "<p style=text-align:center'>$filename was last modified: ".date ("F d Y G:i P ",   filemtime($filename))." GMT";

Answer 2

try this:

 echo "<p style=text-align:center'>$filename was last modified: " .date ("F d Y G:i P ",   filemtime($filename)." GMT");

Answer 3

echo "<p style=text-align:center'>$filename was last modified: " .date ("F d Y G:i P e ", filemtime($filename));