Can't Change Woocommerce "Thank you" message - php

Question

I've tried to edit the thankyou.php file in woocommerce to include some new text, but it keeps on showing the default message. I am not familiar with what anything means in php, but this is what I've been trying:
<?php
/**
* Thankyou page
*
* #author WooThemes
* #package WooCommerce/Templates
* #version 2.2.0
*/
if ( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly
if ( $order ) : ?>
<?php if ( $order->has_status( 'failed' ) ) : ?>
<p><?php _e( 'Unfortunately your order cannot be processed as the originating bank/merchant has declined your transaction.', 'woocommerce' ); ?></p>
<p><?php
if ( is_user_logged_in() )
_e( 'Please attempt your purchase again or go to your account page.', 'woocommerce' );
else
_e( 'Please attempt your purchase again.', 'woocommerce' );
?></p>
<p>
<?php _e( 'Pay', 'woocommerce' ) ?>
<?php if ( is_user_logged_in() ) : ?>
<?php _e( 'My Account', 'woocommerce' ); ?>
<?php endif; ?>
</p>
<?php else : ?>
<p><?php echo apply_filters( 'woocommerce_thankyou_order_received_text', __( 'Your shirt order has been received and will be at your doorstep in approximately 4 weeks. Thanks again for your support (and general badassery)!', 'woocommerce' ), $order ); ?></p>
<ul class="order_details">
<li class="order">
<?php _e( 'Order:', 'woocommerce' ); ?>
<strong><?php echo $order->get_order_number(); ?></strong>
</li>
<li class="date">
<?php _e( 'Date:', 'woocommerce' ); ?>
<strong><?php echo date_i18n( get_option( 'date_format' ), strtotime( $order->order_date ) ); ?></strong>
</li>
<li class="total">
<?php _e( 'Total:', 'woocommerce' ); ?>
<strong><?php echo $order->get_formatted_order_total(); ?></strong>
</li>
<?php if ( $order->payment_method_title ) : ?>
<li class="method">
<?php _e( 'Payment method:', 'woocommerce' ); ?>
<strong><?php echo $order->payment_method_title; ?></strong>
</li>
<?php endif; ?>
</ul>
<div class="clear"></div>
<?php endif; ?>
<?php do_action( 'woocommerce_thankyou_' . $order->payment_method, $order->id ); ?>
<?php do_action( 'woocommerce_thankyou', $order->id ); ?>
<p><?php echo apply_filters( 'woocommerce_thankyou_order_received_text', __( 'Your shirt order has been received and will be at your doorstep in approximately 4 weeks. Thanks again for your support (and general badassery)!', 'woocommerce' ), null ); ?></p>

Answer 1

The best way to do this would be to filter the WC thank you message:
add_filter( 'woocommerce_thankyou_order_received_text', 'd4tw_custom_ty_msg' );
function d4tw_custom_ty_msg ( $thank_you_msg ) {
$thank_you_msg = 'This is your new thank you message';
return $thank_you_msg;
}

Answer 2

Perhaps your theme is overriding your thank you template file. As a general rule you should never edit the plugin directly. Instead move the thankyou.php to your theme. Move this file to wp-content/themes/yourtheme/woocommerce/checkout/thankyou.php. More information it the documentation here.