Rename files during upload within Wordpress - wordpress

Question

I am trying to rename upload filenames match the Post Title.
This other thread shows how to rename to hash:
Rename files during upload within Wordpress backend
Using this code:
function make_filename_hash($filename) {
$info = pathinfo($filename);
$ext = empty($info['extension']) ? '' : '.' . $info['extension'];
$name = basename($filename, $ext);
return md5($name) . $ext;
}
add_filter('sanitize_file_name', 'make_filename_hash', 10);
Does anyone know the code to rename the file to match Post Title.extension?

Answer 1

barakadam's answer is almost correct, just a little correction based on the comment I left below his answer.
function new_filename($filename, $filename_raw) {
global $post;
$info = pathinfo($filename);
$ext = empty($info['extension']) ? '' : '.' . $info['extension'];
$new = $post->post_title . $ext;
// the if is to make sure the script goes into an indefinate loop
if( $new != $filename_raw ) {
$new = sanitize_file_name( $new );
}
return $new;
}
add_filter('sanitize_file_name', 'new_filename', 10, 2);
Explanation of code:
Lets assume you upload a file with the original filename called picture one.jpg to a post called "My Holiday in Paris/London".
When you upload a file, WordPress removes special characters from the original filename using the sanitize_file_name() function.
Right at the bottom of the function is where the filter is.
// line 854 of wp-includes/formatting.php
return apply_filters('sanitize_file_name', $filename, $filename_raw);
At this point, $filename would be picture-one.jpg. Because we used add_filter(), our new_filename() function will be called with $filename as picture-one.jpg and $filename_raw as picture one.jpg.
Our new_filename() function then replaces the filename with the post title with the original extension appended. If we stop here, the new filename $new would end up being My Holiday in Paris/London.jpg which all of us know is an invalid filename.
Here is when we call the sanitize_file_name function again. Note the conditional statement there. Since $new != $filename_raw at this point, it tries to sanitize the filename again.
sanitize_file_name() will be called and at the end of the function, $filename would be My-Holiday-in-Paris-London.jpg while $filename_raw would still be My Holiday in Paris/London.jpg. Because of the apply_filters(), our new_filename() function runs again. But this time, because $new == $filename_raw, thats where it ends.
And My-Holiday-in-Paris-London.jpg is finally returned.

Answer 2

Something like this? (considering $post is your post variable, make it global):
function new_filename($filename) {
global $post;
$info = pathinfo($filename);
$ext = empty($info['extension']) ? '' : '.' . $info['extension'];
return $post->post_title . $ext;
}
add_filter('sanitize_file_name', 'new_filename', 10);
Did I understand you?