Ninja Forms - Copy Fields on Submission: Simplify copying Ninja Forms field values between fields early in the submission. https://www.damiencarbery.com/2019/05/ninja-forms-copy-data-during-submission/

nf-copy-email-to-hidden.php

<?php
/*
Plugin Name: Copy Email field to Hidden
Plugin URI: https://www.damiencarbery.com
Description: Copy the email field to the hidden field using the NinjaFormsCopyFieldsOnSubmission class.
Author: Damien Carbery
Version: 0.1
*/


add_filter( 'nfcf_set_copy_fields', 'dcwd_copy_fields', 10, 3 );
function dcwd_copyfields( $copy_fields, $form_id, $form_data ) {
	if ( 2 == $form_id ) {
		$copy_fields[ 'email_address_field' ] = 'hidden_1558370856218';
	}
	// A different form.
	if ( 5 == $form_id ) {
		$copy_fields[ 'preferred_date_dropdown_asist' ] = 'preferred_date_hidden';
	}
	
	return $copy_fields;
}

nf-copy-fields-on-submission.php

<?php
/*
Plugin Name: Ninja Forms - Copy Fields on Submission
Plugin URI: https://www.damiencarbery.com
Description: Copy Ninja Forms field values during form submission.
Author: Damien Carbery
Version: 0.1
*/


class NinjaFormsCopyFieldsOnSubmission {
	private static $instance;
	private $copy_fields;


	// Returns an instance of this class. 
	public static function get_instance() {
		if ( null == self::$instance ) {
			self::$instance = new NinjaFormsCopyFieldsOnSubmission();
		} 
		return self::$instance;
	}


	// Initialize the plugin variables.
	public function __construct() {
		//$this->form_id = null;
		$this->copy_fields = array();
		//$this->fields_ids = array();

		$this->init();
	}


	// Set up WordPress specfic actions.
	public function init() {
		add_filter( 'ninja_forms_submit_data', array( $this, 'copy_fields' ) );
	}


	public function copy_fields( $form_data ) {
		$this->copy_fields[ 'copy_key_from' ] = 'copy_key_to';  // Initialise with sample data.
		$this->copy_fields = apply_filters( 'nfcf_set_copy_fields', null, $form_data[ 'id' ], $form_data );

		// Shortcut the function if there are no fields to copy in this form.
		if ( empty( $this->copy_fields ) ) {
			return $form_data;
		}
		
		// Store the field keys in an array with the field ID as the value.
		$fields_ids = array();
		foreach ( $form_data[ 'fields' ] as $field ) {
			$fields_ids[ $field[ 'key' ] ] = $field[ 'id' ];
		}

		foreach ($this->copy_fields as $copy_from => $copy_to) {
			// Only copy if both field keys are valid.
			if ( array_key_exists( $copy_from, $fields_ids ) && array_key_exists( $copy_to, $fields_ids ) ) {
				$form_data[ 'fields' ][ $fields_ids[ $copy_to ] ][ 'value' ] = $form_data[ 'fields' ][ $fields_ids[ $copy_from ] ]['value'];
			}
		}

		return $form_data;
	}
}

$NinjaFormsCopyFieldsOnSubmission = new NinjaFormsCopyFieldsOnSubmission();

ninja-forms-submit-data.php

<?php
$form_data = array (
  'id' => '2',
  'fields' => 
  array (
    5 => 
    array (
      'value' => 'My Name Is',
      'id' => 5,
      'key' => 'name_first_field',
    ),
    6 => 
    array (
      'value' => 'damien@damiencarbery.com',
      'id' => 6,
      'key' => 'email_address_field',
    ),
    7 => 
    array (
      'value' => 'Message is here.',
      'id' => 7,
      'key' => 'message_textarea_key',
    ),
    8 => 
    array (
      'value' => '',
      'id' => 8,
      'key' => 'submit',
    ),
    32 => 
    array (
      'value' => '',
      'id' => 32,
      'key' => 'hidden_1558370856218',
    ),
  ),
  );