BuddyForms filter buddyforms_the_author_id to overwrite the author of a post during submission

buddyforms_the_author_id.php

<?php 
//
// Add the auto_assign_user id as post author if auto_assign_user is set for this form
//
add_filter( 'buddyforms_the_author_id', 'buddyforms_auto_assign_user',10 , 2 );
function buddyforms_auto_assign_user($author_id, $form_slug){

	// Check if anonymous author is set
	if( ! isset( $_POST['auto_assign_user'] ) ){
		return $author_id;
	}

	// Check if this form does have an auto_assign_user hidden form element and return the auto_assign_user id from the form element.
	// We not want to make it possible to manipulate this data and not grab it from the form directly.
	$auto_assign_user = buddyforms_get_form_field_by_slug($form_slug, 'auto_assign_user');
	if( isset( $auto_assign_user['value'] ) ){
		return $auto_assign_user['value'];
	}

	return $author_id;

}