Wordpress post repeat twice at the last page - wordpress

Question

I try to display my post using two column, to make sure the fit each other, I tried to create two vertical column, and display the post odd and even seperately. Odd on left side, and even on the right side. And im suing wp_pagenavi() to get navigation working, other page work fine, display the post as I intend it to be, but on the last page, one post will repeat twice.
Here my code for the looping part
<?php if ( have_posts() ) : ?>
<?php /* Start the Loop */ ?>
<div id="holder" class="left">
<?php while ( have_posts() ) : ?>
<?php
$postcount++;
if( ($postcount % 2) == 0 ) : // skip 'even' posts
$wp_query->next_post();
else :
?>
<?php the_post(); ?>
<div class="fpost">
<div class="fposttitle">
<h1 class="left"><?php the_title(); ?></h1>
<?php if ( comments_open() || ( '0' != get_comments_number() && ! comments_open() ) ) : ?>
<div class="combox right">
<?php $x = get_comments_number(); if ($x < 10) : ?>
<?php comments_popup_link( __( '00', 'toolbox' ), __( '01', 'toolbox' ), __( '0%', 'toolbox' ) ); ?>
<?php else : ?>
<?php comments_popup_link( __( '00', 'toolbox' ), __( '01', 'toolbox' ), __( '%', 'toolbox' ) ); ?>
<?php endif; ?>
</div>
<?php endif; ?>
<div class="clear"></div>
</div>
<div class="fcontent">
<?php $thumbnail = get_post_meta(get_the_ID(), 'thumbnail', true);
if ($thumbnail) : ?>
<img src="<?php echo $thumbnail; ?>" alt="<?php the_permalink(); ?>" />
<?php else : ?>
<p><?php the_excerpt(); ?></p>
<?php endif; ?>
</div>
<div class="finfo">
<p class="left date"><?php the_time('F j, Y') ?></p>
<p class="left cat"><?php the_category(', ') ?></p>
<p class="right"><a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Permalink to %s', 'toolbox' ), the_title_attribute( 'echo=0' ) ); ?>" rel="bookmark" >Read More</a></p>
<div class="clear"></div>
</div>
</div>
<?php endif; ?>
<?php endwhile; ?>
</div><!-- #content -->
<div id="holder2" class="left">
<?php while ( have_posts() ) : ?>
<?php
$postcount++;
if( ($postcount % 2) != 0 ) : // skip 'odd' posts
$wp_query->next_post();
else :
?>
<?php the_post(); ?>
<div class="fpost">
<div class="fposttitle">
<h1 class="left"><?php the_title(); ?></h1>
<?php if ( comments_open() || ( '0' != get_comments_number() && ! comments_open() ) ) : ?>
<div class="combox right">
<?php $x = get_comments_number(); if ($x < 10) : ?>
<?php comments_popup_link( __( '00', 'toolbox' ), __( '01', 'toolbox' ), __( '0%', 'toolbox' ) ); ?>
<?php else : ?>
<?php comments_popup_link( __( '00', 'toolbox' ), __( '01', 'toolbox' ), __( '%', 'toolbox' ) ); ?>
<?php endif; ?>
</div>
<?php endif; ?>
<div class="clear"></div>
</div>
<div class="fcontent">
<?php $thumbnail = get_post_meta(get_the_ID(), 'thumbnail', true);
if ($thumbnail) : ?>
<img src="<?php echo $thumbnail; ?>" alt="<?php the_permalink(); ?>" />
<?php else : ?>
<p><?php the_excerpt(); ?></p>
<?php endif; ?>
</div>
<div class="finfo">
<p class="left date"><?php the_time('F j, Y') ?></p>
<p class="left cat"><?php the_category(', ') ?></p>
<p class="right"><a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Permalink to %s', 'toolbox' ), the_title_attribute( 'echo=0' ) ); ?>" rel="bookmark" >Read More</a></p>
<div class="clear"></div>
</div>
</div>
<?php endif; ?>
<?php endwhile; ?>
</div><!-- #content -->
<?php else : ?>
no post
<?php endif; ?>
<div class="clear"></div>
<div id="nav"> <?php wp_pagenavi() ?> </div>
</div><!-- #primary -->
I thinking maybe because last page, there is not enough number post, but can't figure out why the post repeat.
update: I just tried to add one new post, and everything work fine. but when I add another post, it the last page repeat same post again.

Answer 1

Probably should have included this as an answer instead of a comment, in the case where you have an odd number of posts, you don't reset your $postcount variable to 0, so your 2nd loop doesn't necessarily start on the same condition that the first loop did. So on your last page you're able to notice this happening, but chances are on the other pages you're skipping certain posts altogether:
<?php if ( have_posts() ) : ?>
<?php /* Start the Loop */ ?>
<div id="holder" class="left">
<?php $postcount = 0; ?>
<?php while ( have_posts() ) : ?>
<?php
$postcount++;
if( ($postcount % 2) == 0 ) : // skip 'even' posts
$wp_query->next_post();
else :
?>
<?php the_post(); ?>
<?php endif; ?>
<?php endwhile; ?>
...
</div><!-- #content -->
<div id="holder2" class="left">
<?php $postcount = 0; ?>
<?php rewind_posts();//rewind the post counter so you can do another loop ?>
<?php while ( have_posts() ) : ?>
<?php
$postcount++;
if( ($postcount % 2) != 0 ) : // skip 'odd' posts
$wp_query->next_post();
else :
?>
<?php the_post(); ?>
...
<?php endif; ?>
<?php endwhile; ?>
</div><!-- #content -->