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

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;        
}