最简单的方法是劫持gallery短代码（不需要额外的正则表达式），将其存储在某处并添加到末尾。

原型

<?php # -*- coding: utf-8 -*-
/**
 * Plugin Name: T5 Move Galleries To End Of Content
 */
add_action( \'after_setup_theme\', array ( \'T5_Move_Galleries\', \'init\' ) );

class T5_Move_Galleries
{
    public static $galleries = array();

    /**
     * Re-order gallery shortcodes and register the content filter.
     */
    public static function init()
    {
        remove_shortcode( \'gallery\', \'gallery_shortcode\' );
        add_shortcode( \'gallery\', array ( __CLASS__, \'catch_gallery\' ) );
        // Note the priority: This must run after the shortcode parser.
        add_filter( \'the_content\', array ( __CLASS__, \'print_galleries\' ), 100 );
    }

    /**
     * Collect the gallery output. Stored in self::$galleries.
     *
     * @param array $attr
     */
    public static function catch_gallery( $attr )
    {
        self::$galleries[] = gallery_shortcode( $attr );
    }

    /**
     * Append the collected galleries to the content.
     *
     * @param  string $content
     * @return string
     */
    public static function print_galleries( $content )
    {
        return $content . implode( \'\', self::$galleries );
    }
}