ctp extension is used by the CakePHP as an extension of their template files.
There is not any special with them they are plain HTML/PHP files just they have this ctp extension.
I think it would be useful to open these files with the proper highlighting.

• Create a file with the following contents:

Hello world!<br>
<?php echo "PHP sys hello too"; ?>

• Save as foo.ctp
• Open with Kate
• The highlighting should highlight the <?php and the ?> tags at least.