how to display wordpress post excerpt only on the image post which has excerpt on hover

Question

I have created a gridview of wordpress posts, and i am trying to display excerpt on mouse hover for each thumbnail(post) but if any thumbnail(post) don't have any excerpt content it should not display that.

    <?php
    $args = array('post_type' => 'press');

    $counter = 1; //start counter

    $grids = 4; //Grids per row

    global $query_string; //Need this to make pagination work


    /*Setting up our custom query (In here we are setting it to show 12 posts per page and eliminate     all sticky posts) */
    query_posts ( $args );//query_posts($query_string . '&caller_get_posts=6&posts_per_page=12');

    if(have_posts()) :  while(have_posts()) :  the_post(); 
    ?>
    <?php
    //Show the left hand side column
if($counter >= 1) :
?>
        <div class="griditemleft" style="position:relative;">
        <div class="postimage">
            <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_post_thumbnail('category-thumbnail'); ?></a>
<div class="excerpt"><?php if post have excerpt then display .excerpt on hover else display only the thumbnail?>
        </div>
        <h2 class="press-title"><a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
    </div>
                <h2 class="press-title"><a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
            </div>
<?php
//Show the right hand side column
elseif($counter == $grids) :
?>

<div class="clear"></div>
<?php
$counter = 0;
endif;
?>
<?php
$counter++;
endwhile;
//Pagination can go here if you want it.
endif;
?>

Answer 1

If I understand you correctly, you want don't want to display a post if there is no thumbnail associated with it. If I am right, then what you should do is add another condition in the if statement ( if($counter >= 1) ). add this condition (get_post_thumbnail() !== ") to the current if statement and it should do as you desire. Example is below:

if(($counter >= 1 && (get_post_thumbnail() !== ""))

Edit: After reading what what you have added. I would suggest that you use the get_the_excerpt() function . It returns a value if there is an excerpt present, otherwise it returns an empty string. Check out the code example below:

$my_excerpt = get_the_excerpt();
if ( $my_excerpt != '' ) {
    // print excerpt
}

Using this code and some JavaScript or CSS, you should be able to achieve your desired effect.