How to add a custom attribute?

Question

How to add a custom attribute in the field Contact Form 7 without javascript ?

For example, there is such a field on the page:

Answer 1

Extending on from Tofandel's solution, for the benefit of those who got 99% of the way there, but suffered validation issues - I've resolved that in my case and would like to offer an extended solution that gets as far as Tofandel's (putting the attribute into the form proper) but also successfully validates on submission.

    add_filter('wpcf7_form_tag', function($tag) {
      $data = [];
      foreach ((array)$tag['options'] as $option) {
        if (strpos( $option, 'autocomplete') === 0) {
          $option = explode(':', $option, 2);
          $data[$option[0]] = apply_filters('wpcf7_option_value', $option[1], $option[0]);
        }
      }
      if(!empty($data)) {
        add_filter('wpcf7_form_elements', function ($content) use ($tag, $data) {
          $data_attrs = wpcf7_format_atts($data);
          $name = $tag['name'];
          $content_plus_data_attrs = str_replace("name=\"$name\"", "name=\"$name\" " . $data_attrs, $content);

          return $content_plus_data_attrs;
        });
      }
      return $tag;
    } );

Rather than changing the tag ID to a random value only to replace it with the "real" value later, we just reference the real value in the first place, replacing the relevant part of the content in the wpcf7_form_elements filter (in my case, autocomplete, but as Tofandel's example shows, this can be extended to any data attribute you'd like).

Answer 2

Here is a generic solution that doesn't involve hardcoding the field name and the attributes

add_filter( 'wpcf7_form_tag', function ( $tag ) {
    $datas = [];
    foreach ( (array)$tag['options'] as $option ) {
        if ( strpos( $option, 'data-' ) === 0 ) {
            $option = explode( ':', $option, 2 );
            $datas[$option[0]] = apply_filters('wpcf7_option_value', $option[1], $option[0]);
        }
    }
    if ( ! empty( $datas ) ) {
        $name = $tag['name'];
        $tag['name'] = $id = uniqid('wpcf');
        add_filter( 'wpcf7_form_elements', function ($content) use ($name, $id, $datas) {
            return str_replace($id, $name, str_replace("name=\"$id\"", "name=\"$name\" ". wpcf7_format_atts($datas), $content));
        });
    }
    return $tag;
} );

It works on all data attributes so you can use it like this

[text* my-name data-foo:bar data-biz:baz placeholder "Blabla"]
Output: <input type="text" name="my-name" data-foo="bar" data-biz="baz" placeholder="Blabla">

Since wpcf7 doesn't provide a way to hook into options directly the solutions uses a trick and temporary replaces the name of the field by a unique id that is then replaced in a later filter with the correct name and added attributes

If you need it to work with more than just data attributes you can whitelist some more attributes by replacing this line

if ( strpos( $option, 'data-' ) === 0 ) {

to something like the following

if ( preg_match( '/^(data-|pattern|my-custom-attribute)/', $option ) ) {

Answer 3

Multiple attributes can be added also. eg

add_filter( 'wpcf7_form_elements', 'imp_wpcf7_form_elements' );

function imp_wpcf7_form_elements( $content ) {
    $str_pos = strpos( $content, 'name="your-email-homepage"' );
    $content = substr_replace( $content, ' aria-describedby="emailHelp" ', $str_pos, 0 );

    $str_pos2 = strpos( $content, 'name="your-fname-homepage"' );
    $content = substr_replace( $content, ' aria-describedby="fnameHelp" ', $str_pos2, 0 );

    $str_pos3 = strpos( $content, 'name="your-lname-homepage"' );
    $content = substr_replace( $content, ' aria-describedby="lnameHelp" ', $str_pos3, 0 );
    return $content;        
}

Answer 4

Find the name of your field.

[text* text-21]

If the name of your field name="text-21", like in my example, add this code to functions.php file.

add_filter( 'wpcf7_form_elements', 'imp_wpcf7_form_elements' );
function imp_wpcf7_form_elements( $content ) {
    $str_pos = strpos( $content, 'name="text-21"' );
    if ( $str_pos !== false ) {
        $content = substr_replace( $content, ' data-attr="custom" data-msg="Foo Bar 1" ', $str_pos, 0 );
    }
    return $content;
}

Note, it will add those attributes to all forms elements where the name is text-21, if you want prevent it then give your form element some unique name [text* unique-name]

And change the code to

add_filter( 'wpcf7_form_elements', 'imp_wpcf7_form_elements' );
function imp_wpcf7_form_elements( $content ) {
    $str_pos = strpos( $content, 'name="unique-name"' );
    if ( $str_pos !== false ) {
        $content = substr_replace( $content, ' data-attr="custom" data-msg="Foo Bar 1" ', $str_pos, 0 );
    }
    return $content;
}