查看函数的声明：

function add_settings_field(
    $id,
    $title,
    $callback,
    $page,
    $section = \'default\',
    $args    = array()
) { }

我的插件示例Public Contact Data

    foreach ( $this->fields as $type => $desc )
    {
        $handle   = $this->option_name . "_$type";
        $args     = array (
            \'label_for\' => $handle,
            \'type\'      => $type
        );
        $callback = array ( $this, \'print_input_field\' );

        add_settings_field(
            $handle,
            $desc,
            $callback,
            \'general\',
            \'default\',
            $args
        );
    }

/**
 * Input fields in \'wp-admin/options-general.php\'
 *
 * @see    add_contact_fields()
 * @param  array $args Arguments send by add_contact_fields()
 * @return void
 */
public function print_input_field( array $args )
{
    $type   = $args[\'type\'];
    $id     = $args[\'label_for\'];
    $data   = get_option( $this->option_name, array() );
    $value  = $data[ $type ];

    \'email\' == $type and \'\' == $value and $value = $this->admin_mail;
    $value  = esc_attr( $value );
    $name   = $this->option_name . \'[\' . $type . \']\';
    $desc   = $this->get_shortcode_help( $type );

    print "<input type=\'$type\' value=\'$value\' name=\'$name\' id=\'$id\'
        class=\'regular-text code\' /> <span class=\'description\'>$desc</span>";
}