我正在使用下面的代码通过WordPress循环挑选最新的帖子，但它在full 尺寸：

if ( have_posts() ) :
    while ( have_posts() ) : the_post(); ?>
        <!-- Post Start -->
        <div id="post">
            <a class="post_image" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
                <?php if ( has_post_thumbnail() ):
                    the_post_thumbnail(\'full\');
                else : ?>
                    <img src="<?php echo get_template_directory_uri(); ?>/images/No-Thumbnail-Available.png" alt="<?php the_title(); ?>" />
                <?php endif; ?>
            </a>
            <h2 class="post_title"><a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a></h2>
            <span class="post_desc"><?php the_excerpt(); ?></span>
            <div class="clear"></div>
        </div>
        <!-- Post Start -->
    <?php endwhile;
else: ?>
    <p class="error"><?php _e(\'Sorry, No Article Is Available Here...\'); ?></p>
<?php endif;

我想挑选full 循环的第一个帖子的图像，以及thumbnail 循环中所有其他帖子的图像。我可以通过CSS做到这一点，但这对SEO不友好。我正在使用以下代码，但它不起作用：

$first = true;
foreach ( $obj as $value ) {
    if ( $first ) { ?>
        <!-- Post Start -->
        <div id="post">
            <a class="post_image" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
                <?php if ( has_post_thumbnail() ):
                    the_post_thumbnail(\'full\');
                else : ?>
                    <img src="<?php echo get_template_directory_uri(); ?>/images/No-Thumbnail-Available.png" alt="<?php the_title(); ?>" />
                <?php endif; ?>
            </a>
            <h2 class="post_title"><a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a></h2>
            <span class="post_desc"><?php the_excerpt(); ?></span>
            <div class="clear"></div>
        </div>
        <!-- Post Start -->
        <?php $first = false;
    } else { ?>
        <!-- Post Start -->
        <div id="post">
            <a class="post_image" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
                <?php if ( has_post_thumbnail() ):
                    the_post_thumbnail(\'thumbnail\');
                else : ?>
                    <img src="<?php echo get_template_directory_uri(); ?>/images/No-Thumbnail-Available.png" alt="<?php the_title(); ?>" />
                <?php endif; ?>
            </a>
            <h2 class="post_title"><a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a></h2>
            <span class="post_desc"><?php the_excerpt(); ?></span>
            <div class="clear"></div>
        </div>
        <!-- Post Start -->
    <?php }
}

<?php 
$i = 0;
while ( have_posts() ) : the_post();
    $i++;
    if ( $i == 1 ): ?>
    <!-- First Post -->
    <div id="post">
        <a class="post_image" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
            <?php if ( has_post_thumbnail() ): ?>
                <?php the_post_thumbnail(\'full\'); ?>
            <?php else : ?>
                <img src="<?php echo get_template_directory_uri(); ?>/images/No-Thumbnail-Available.png" alt="<?php the_title(); ?>" />
            <?php endif; ?>
        </a>
        <h2 class="post_title"><a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a></h2>
        <span class="post_desc"><?php the_excerpt(); ?></span>
        <div class="clear"></div>
    </div>
<?php else: // else $i == 1 ?>
    <!-- All Other Posts -->
    <div id="post">
        <a class="post_image" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
            <?php if ( has_post_thumbnail() ): ?>
                <?php the_post_thumbnail(\'thumbnail\'); ?>
            <?php else : ?>
                <img src="<?php echo get_template_directory_uri(); ?>/images/No-Thumbnail-Available.png" alt="<?php the_title(); ?>" />
            <?php endif; ?>
        </a>
        <h2 class="post_title"><a href="<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a></h2>
        <span class="post_desc"><?php the_excerpt(); ?></span>
        <div class="clear"></div>
    </div>
<?php endif; // endif for $i == 1 ?>
<?php endwhile; ?>