Using php to rename all files in folder - php

Question

new php programmer here. I have been trying to rename all the files in a folder by replacing the extension.
The code I'm using is from the answer to a similar question on SO.
if ($handle = opendir('/public_html/testfolder/')) {
while (false !== ($fileName = readdir($handle))) {
$newName = str_replace(".php",".html",$fileName);
rename($fileName, $newName);
}
closedir($handle);
}
I get no errors when running the code, but no changes are made to the filenames.
Any insight on why this isn't working? My permission settings should allow it.
Thanks in advance.
EDIT: I get a blank page when checking the return value of rename(), now trying something with glob() which might be a better option than opendir...?
EDIT 2: With the 2nd code snippet below, I can print the contents of $newfiles. So the array exists, but the str_replace + rename() snippet fails to change the filename.
$files = glob('testfolder/*');
foreach($files as $newfiles)
{
//This code doesn't work:
$change = str_replace('php','html',$newfiles);
rename($newfiles,$change);
// But printing $newfiles works fine
print_r($newfiles);
}

Answer 1

Here is the simple solution:
PHP Code:
// your folder name, here I am using templates in root
$directory = 'templates/';
foreach (glob($directory."*.html") as $filename) {
$file = realpath($filename);
rename($file, str_replace(".html",".php",$file));
}
Above code will convert all .html file in .php

Answer 2

You're probably working in the wrong directory. Make sure to prefix $fileName and $newName with the directory.
In particular, opendir and readdir don't communicate any information on the present working directory to rename. readdir only returns the file's name, not its path. So you're passing just the file name to rename.
Something like below should work better:
$directory = '/public_html/testfolder/';
if ($handle = opendir($directory)) {
while (false !== ($fileName = readdir($handle))) {
$newName = str_replace(".php",".html",$fileName);
rename($directory . $fileName, $directory . $newName);
}
closedir($handle);
}

Answer 3

Are you sure that
opendir($directory)
works? Have you checked that? Because it seems there might be some Document Root missing here...
I would try
$directory = $_SERVER['DOCUMENT_ROOT'].'public_html/testfolder/';
And then Telgin's solution:
if ($handle = opendir($directory)) {
while (false !== ($fileName = readdir($handle))) {
$newName = str_replace(".php",".html",$fileName);
rename($directory . $fileName, $directory . $newName);
}
closedir($handle);
}

Answer 4

That happens if the file is opened. Then php cannot do any changes to the file.

Answer 5

<?php
$directory = '/var/www/html/myvetrx/media/mydoc/';
if ($handle = opendir($directory)) {
while (false !== ($fileName = readdir($handle))) {
$dd = explode('.', $fileName);
$ss = str_replace('_','-',$dd[0]);
$newfile = strtolower($ss.'.'.$dd[1]);
rename($directory . $fileName, $directory.$newfile);
}
closedir($handle);
}
?>
Thank you so much for the suggestions. it's working for me!