Set WordPress user email instead of billing email as default value for WooCommerce checkout field

Question

What I am trying to do is change the checkout fields so that if a user is logged in they can't edit their billing email field.

This code below works great however ideally I want to remove the situation where users are able to have 2 email address in the first place and set the value of $address_fields['billing']['billing_email'] to be the users email address from their account.

I've tried adding

'value' => $current_user->user_email

and

'default' => $current_user->user_email

to the array however this appears to do nothing.

So:

1. Firstly, how can I set a value for this form and prevent it from being changed.
2. Secondly, is $current_user->user_email the correct way to get the users account (contact) email and not the billing email from their account.

function custom_checkout_fields( $address_fields ) {
    
    
    $current_user = wp_get_current_user();
    
    if ( is_user_logged_in() ) {
        unset( $address_fields['billing']['billing_email'] );
        unset( $address_fields['billing']['billing_em_ver'] );
    
    $address_fields['billing']['billing_email'] = [
            'label' => 'Email address',
            'required'  => false,
            'description'   =>  '<i><a href="/shop/my-account/customer-logout/">to change this please click here logout and login/register as another user</a> or <a href="/shop/my-account/edit-account/">click here to modify the address on your account</a></i>',
            'custom_attributes' => [
                'disabled' => 'disabled',
            ]
        ];
    
    
    
        return $address_fields;
    } else{
    return $address_fields;
    }
    }
    add_filter( 'woocommerce_checkout_fields', 'custom_checkout_fields' ,20, 1 );

Answer 1

Firstly, go to /plugins/woocommerce/templates/checkout, copy the form-billing.php template file found in that folder and paste it in yourTheme/woocommerce/checkout/.

Secondly, prevent WooCommerce from auto-filling the email address field by editing the copied form-billing.php template file and changing the following snippet:

    <div class="woocommerce-billing-fields__field-wrapper">
      <?php
      $fields = $checkout->get_checkout_fields( 'billing' );

      foreach ( $fields as $key => $field ) {
        woocommerce_form_field( $key, $field, $checkout->get_value( $key ) );
      }
      ?>
    </div>

To this:

    <div class="woocommerce-billing-fields__field-wrapper">
      <?php
      $fields = $checkout->get_checkout_fields( 'billing' );

      foreach ( $fields as $key => $field ) {
        if ( 'billing_email' != $key ) {
            woocommerce_form_field( $key, $field, $checkout->get_value( $key ) );
        } else {
            woocommerce_form_field( $key, $field );
        }
      }
      ?>
    </div>

Thirdly, inject the WordPress email to the field, make it immutable and add your custom description by adding the following to your theme's functions.php file:

function shillongtitude_billing_email_field($fields) {
  
  if ( is_user_logged_in() ) {

    $current_user = wp_get_current_user();

    //set the user email as the email field value
    $fields['billing']['billing_email']['default'] = $current_user->user_email;
    
    //set the description
    $fields['billing']['billing_email']['description'] = '<i><a href="/shop/my-account/customer-logout/">to change this please click here logout and login/register as another user</a> or <a href="/shop/my-account/edit-account/">click here to modify the address on your account</a></i>';
    
    // set attributes
    $fields['billing']['billing_email']['custom_attributes'] = array( 'readonly'=>'readonly', 'label' => 'Email address', 'required' => false );
            
    return $fields;
  } else {
    return $fields;
  }
}
add_filter('woocommerce_checkout_fields', 'shillongtitude_billing_email_field');