Generate Unique ID

/*
 * Create a unique ID with a specific number of characters and assign it to each form submission.
 *
 * @link https://wpforms.com/developers/how-to-create-a-unique-id-for-each-form-entry/
 */

// Generate Unique ID Smart Tag for WPForms
function wpf_dev_register_smarttag( $tags ) {

    // Key is the tag, item is the tag name.
    $tags[ 'unique_id' ] = 'Unique ID';

    return $tags;
}

/*
 *  Generate Random 3char string
 */
 function randStr($chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', $length = 3) {
    return substr(str_shuffle($chars), 0, $length);
}

/*
 * Generate random 3 digit number
 */

 function randNum($chars = '0123456789', $length = 3) {
    return substr(str_shuffle($chars), 0, $length);
}

/*
 *  Generate Output
 */

function generateOutput() {
    $output = randStr() . randNum();
    return $output;
}


add_filter( 'wpforms_smart_tags', 'wpf_dev_register_smarttag' );

// Generate Unique ID value
function wpf_dev_process_smarttag( $content, $tag, $form_data, $fields, $entry_id ) {

    // Only run if it is our desired tag.
    if ( 'unique_id' === $tag && !$entry_id ) {

    // generate a hexadecimal string based on the time to ensure uniqueness
    // reduce the string to 6 characters
    $uuid = randStr() . randNum();

        // Replace the tag with our Unique ID.
        $content = str_replace( '{unique_id}', $uuid, $content );
    } elseif ( 'unique_id' === $tag && $entry_id ) {

        foreach ($form_data[ 'fields' ] as $field) {

            if ( preg_match('/\b{unique_id}\b/', $field[ 'default_value' ]) ) {
                $field_id = $field[ 'id' ];
                break;
            }

        }

        $content = str_replace( '{unique_id}', $fields[$field_id][ 'value' ], $content);
    }

    return $content;
}

add_filter( 'wpforms_smart_tag_process', 'wpf_dev_process_smarttag', 10, 5 );