Here is my solution with substr() function in PHP:
<?php
//C:\Internal\training-internal\Template.pptx
$fullFileName = readline();
$lastSlash = strrpos($fullFileName, "\\");//Escape the \
$file = substr($fullFileName, $lastSlash + 1);
//$file = Template.pptx
$lastDot = strrpos($file, ".");
$fileExtension = substr($file, $lastDot + 1);//pptx
$fileName = substr($file, 0, $lastDot);//Template
echo "File name: " . $fileName.PHP_EOL;
echo "File extension: " . $fileExtension;
And some screenshots of some of the string functions in PHP:

Here is a link to a video explaining the substr() function: https://www.youtube.com/watch?v=FIoQb0inLEM
...and 2 replace functions in PHP:
