我正在尝试构建一个短代码，允许用户选择显示的类别和显示的帖子数量。在我添加“tax\\u查询”之前，该短代码运行良好

add_shortcode( \'latest_post\', \'latest_post_query_shortcode\' );
function latest_post_query_shortcode(  $atts ) {
    $atts = shortcode_atts( array(
            \'post_per_page\' => \'\',
            \'category\' => \'\',
    ), $atts );

    $args = array(
            \'post_type\'     => \'post\',
            \'post_status\'   => \'publish\',
            \'posts_per_page\'=> 3,
            \'tax_query\'     => array( array(
                                \'taxonomy\'  => \'category\',
                                \'field\'     => \'slug\',
                                \'terms\'     => $categories
                            ), ),
        );

        $string = \'\';
    // The Query
    $query = new WP_Query( $args ); 

    // The Loop
    if ( $query->have_posts() ) { ?>
        <section class="recent-posts clear">
        <?php while ( $query->have_posts() ) : $query->the_post() ; ?>
            <article id="post-<?php the_ID(); ?>" <?php post_class( \'left\' ); ?>>
                <? echo \'<a href="\' . get_permalink( $_post->ID ) . \'" title="\' . esc_attr( $_post->post_title ) . \'">\';
                    echo get_the_title( $_post->ID);
                    echo \'</a>\';
                    echo \'<a href="\' . get_permalink( $_post->ID ) . \'" title="\' . esc_attr( $_post->post_title ) . \'">\';
                    echo get_the_post_thumbnail( $_post->ID, \'medium\' );
                    echo \'</a>\';
                    echo \'<a href="\' . get_permalink( $_post->ID ) . \'" title="\' . esc_attr( $_post->post_title ) . \'">\';
                    echo \'<button>Read More</button>\';
                    echo \'</a>\';
                ?>

            </article>
        <?php endwhile; ?>
        </section>
    <?php } else {
        echo \'No posts found\';
    }
    /* Restore original Post Data */
    wp_reset_postdata();
}

在添加tax\\u查询之前，它将显示三个最新的帖子，而tax\\u查询只显示“找不到帖子”我做错了什么？