Auto Increment Custom Post Type Title - php

Question

I created a custom post type "Testimonials" and removed support for the title. I am wanting to auto increment the title such as Testimony #1, Testimony #2, Testimony #3, etc.. right now it saves as "auto draft". Any help would be appreciated.
BTW I am not echoing the title, it will only be visible by me.

Answer 1

Made some improvements to the code provided #the-alpha.
// Use a filter to make the change
add_filter( 'wp_insert_post_data' , 'modify_post_title' , '99', 2 );
function modify_post_title( $data , $postarr ) {
// Check for the custom post type and if it's in trash
// We only need to modify if it when it's going to be published
$posts_status = ['publish', 'future', 'draft', 'pending', 'private', 'trash'];
if( $data['post_type'] == 'oferta' && !in_array($data['post_status'], $posts_status)) {
// Count the number of posts to check if the current post is the first one
$count_posts = wp_count_posts('you custom post type');
$published_posts = $count_posts->publish;
// Check if it's the first one
if ($published_posts == 0) {
$data['post_title'] = date('Y-m') . '-1';
} else {
// Get the most recent post
$args = array(
'numberposts' => 1,
'orderby' => 'post_date',
'order' => 'DESC',
'post_type' => 'you custom post type',
'post_status' => 'publish'
);
$last_post = wp_get_recent_posts($args);
// Get the title
$last_post_title = $last_post['0']['post_title'];
// Get the title and get the number from it.
// We increment from that number
$number = explode('-', $last_post_title);
$number = $number[2] + 1;
// Save the title.
$data['post_title'] = date('Y-m') . '-' . $number;
}
}
return $data;
}
In this case the user doesn't have the ability to modify the custom post type title and whole thing increments based on the title.

Answer 2

on post submission from frontend custom post title set to #1 but not increment to #2 on second post submission..
This is the exact code used in functions.php
add_filter( 'wp_insert_post_data' , 'modify_post_title' , '99', 2 );
function modify_post_title( $data , $postarr )
{
if( $data['post_type'] == 'your custom post type' ) {
$last_post = wp_get_recent_posts( '1');
$last__post_id = (int)$last_post['0']['ID'];
$data['post_title'] = 'Testimony #' . ($last__post_id+1);
}
return $data;
}