Posts in the developer's cookbook category describe topics that require technical knowledge. Be warned and use the techniques at your own risk. Unless you are an experienced developer, you are strongly advised to ask a professional for support.

A mail-tag has a corresponding form-tag; when an email is composed, a mail-tag in the email template is replaced with the user input value that comes through the input field represented by the corresponding form-tag.

By default a mail-tag is replaced with the raw value the submitter inputs. You are able to customize this mail-tag replacement. To do this you use the wpcf7_mail_tag_replaced filter hook, as shown in the following example:

add_filter( 'wpcf7_mail_tag_replaced',

  function( $replaced, $submitted, $html, $mail_tag ) {
    if ( is_numeric( $submitted ) ) {
      $replaced = number_format( $submitted );
    }

    return $replaced;
  },

  10, 4
);

This filter function (notice that examples in this post use anonymous functions that are available in PHP 5.3 and higher) formats numerical values using the number_format function. When “1234567890” is the user input you will see “1,234,567,890” in the email message.

The wpcf7_mail_tag_replaced filter hook passes four parameters to a hooked function: $replaced, $submitted, $html, and $mail_tag.

$replaced has the value generated as the result of mail-tag replacement.

$submitted has the original value that has been input by the submitter.

$html has a boolean value; true if the mail-tag is used in an HTML message body.

$mail_tag has a WPCF7_MailTag object that represents the mail-tag itself.

Targeting a specific field

In the above example code the number_format function was applied to every field where the input was a numerical value. If you want to target a specific field you can do so by using the fourth $mail_tag argument, like in this example:

add_filter( 'wpcf7_mail_tag_replaced',

  function( $replaced, $submitted, $html, $mail_tag ) {
    if ( 'your-number' == $mail_tag->field_name() ) {
      if ( is_numeric( $submitted ) ) {
        $replaced = number_format( $submitted );
      }
    }

    return $replaced;
  },

  10, 4
);

By doing it this way the number_format is applied only when the field name of the mail-tag is ‘your-number’.

Targeting a specific form-tag type

There are variants of the wpcf7_mail_tag_replaced filter hook that are applied only to mail-tags corresponding to form-tags of a specific form-tag type. These filter hooks have the form-tag type as a suffix.

For example, use the wpcf7_mail_tag_replaced_number hook when you want to target form-tags of the number type:

add_filter( 'wpcf7_mail_tag_replaced_number',

  function( $replaced, $submitted, $html, $mail_tag ) {
    if ( is_numeric( $submitted ) ) {
      $replaced = number_format( $submitted );
    }

    return $replaced;
  },

  10, 4
);