title: How to check email exist Wordpress
body: <p>I create custom filed in checkout page in woocommerce to add Reagent user email:</p>
  
  <pre><code>add_action( 'woocommerce_after_order_notes', 'my_custom_checkout_field' );
  
  function my_custom_checkout_field( $checkout ) {
  
  
      woocommerce_form_field( 'my_field_name', array(
          'type'          =&gt; 'text',
          'class'         =&gt; array('my-field-class form-row-wide'),
          'label'         =&gt; __('ایمیل معرف'),
          'placeholder'   =&gt; __('ایمیل معرف خود را وارد کنید'),
          ), $checkout-&gt;get_value( 'my_field_name' ));
  
      echo '&lt;/div&gt;';
      return $checkout;
  
  
  }
  </code></pre>
  
  <p>So now i want get error if the Reagent user email not exist.</p>
  
  <p>i using the code:</p>
  
  <pre><code>add_filter('my_custom_checkout_field', 'yourprefix_process_myaccount_address_fields' );
  
  function yourprefix_process_myaccount_address_fields( $checkout ) {
       $exists = email_exists($checkout);
    if ( $exists )
      echo "That E-mail is registered to user number" . $exists;
    else
          wc_add_notice( __( 'Email not exist', 'woocommerce' ), 'error' );
      }
  }
  </code></pre>
  
  <p>but the code not working and not get any errror...
   so how can do it?</p>