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/**
 * to exclude field from notification add 'exclude[ID]' option to {all_fields} tag
 * 'include[ID]' option includes HTML field / Section Break field description / Signature image in notification
 * see http://www.gravityhelp.com/documentation/page/Merge_Tags for a list of standard options
 * example: {all_fields:exclude[2,3]}
 * example: {all_fields:include[6]}
 * example: {all_fields:include[6],exclude[2,3]}
 */
add_filter( 'gform_merge_tag_filter', 'all_fields_extra_options', 11, 5 );
function all_fields_extra_options( $value, $merge_tag, $options, $field, $raw_value ) {
    if ( $merge_tag != 'all_fields' ) {
        return $value;
    }

    // usage: {all_fields:include[ID],exclude[ID,ID]}
    $include = preg_match( "/include\[(.*?)\]/", $options , $include_match );
    $include_array = explode( ',', rgar( $include_match, 1 ) );

    $exclude = preg_match( "/exclude\[(.*?)\]/", $options , $exclude_match );
    $exclude_array = explode( ',', rgar( $exclude_match, 1 ) );

    $log = "all_fields_extra_options(): {$field['label']}({$field['id']} - {$field['type']}) - ";

    if ( $include && in_array( $field['id'], $include_array ) ) {
        switch ( $field['type'] ) {
            case 'html' :
                $value = $field['content'];
                break;
            case 'section' :
                $value .= sprintf( '<tr bgcolor="#FFFFFF">
                                                        <td width="20">&nbsp;</td>
                                                        <td>
                                                            <font style="font-family: sans-serif; font-size:12px;">%s</font>
                                                        </td>
                                                   </tr>
                                                   ', $field['description'] );
                break;
            case 'signature' :
                $url = GFSignature::get_signature_url( $raw_value );
                $value = "<img alt='signature' src='{$url}'/>";
                break;
        }
        GFCommon::log_debug( $log . 'included.' );
    }
    if ( $exclude && in_array( $field['id'], $exclude_array ) ) {
        GFCommon::log_debug( $log . 'excluded.' );
        return false;
    }
    return $value;
}