ninja_forms_pre_process

ninja_forms_pre_process.php

<?php
function ninja_forms_register_example(){
  add_action( 'ninja_forms_pre_process', 'ninja_forms_example' );
}
add_action( 'init', 'ninja_forms_register_example' );

function ninja_forms_example(){
  global $ninja_forms_processing;
  
  //Get the user submitted value for the field with an ID of 3.
  $user_value = $ninja_forms_processing->get_field_value( 3 );
  
  //Add the text Hello World to the user value.
  $user_value .= "Hello World";
  
  //Update the user submitted value for the field with an ID of 3:
  $ninja_forms_processing->update_field_value( 3, $user_value );

}