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I have a post thumbnail set for standard posts (when an image is featured) but for image format posts I'd like to have a separate, dynamically resizing (i.e. image resizing in the functions php via add_image_size), thumbnail. I found this snippet from the codex:

if ( has_post_format( 'video' )) {
echo 'this is the video format';

I've tried using it on my index.php with 0 success. Am I on the right track or should I be doing something completely different?

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What do you mean by, "dynamically resizing, thumbnail"? The intermediate image sizes are static. – Chip Bennett Mar 9 '12 at 0:59
This is all I meant: add_image_size( 'index-thumb', 640, 250, true ); add_image_size( 'image-format', 630, 9999, true ); – Colton Allen Mar 9 '12 at 1:00
So is your issue that you don't see that text echoing on the index.php page? or are you lacking the code to display your custom image size? – Michelle Mar 9 '12 at 1:05
I tried echoing php has_post_thumbnail blah blah and it ended up completely rearranging the index page's structure in really weird ways so I just presumed it wouldn't work that way. – Colton Allen Mar 9 '12 at 1:18
up vote 0 down vote accepted

From your comment:

This is all I meant: add_image_size( 'index-thumb', 640, 250, true ); add_image_size( 'image-format', 630, 9999, true );

So, let's assume you create custom image sizes for gallery and video (as well as a "default" size, which we'll call standard), perhaps like so:

add_image_size( 'index-standard', 640, 250, true );
add_image_size( 'image-gallery', 630, 9999, true );
add_image_size( 'image-video', 700, 9999, true );

Now, in your template, where you want to output the custom image size, let's figure out which one to use, via get_post_format(), like so:

// Determine post format
$post_format = ( get_post_format() ? get_post_format() : 'standard' );
// Set image size based on post format
$thumbnail_size = 'image-' . $post_format;
// Output post thumbnail
the_post_thumbnail( $thumbnail_size );

That should be it.

Note: By using get_post_format(), all you have to do is register the image size for each supported format, and you're done. You can use has_post_format(), but you'd have to add explicit code for each supported format, like so:

$thumbnail_size = 'image-standard';
if ( has_post_format( 'gallery' ) ) {
    $thumbnail_size = 'image-gallery';   
} else if ( has_post_format( 'video' ) ) {
    $thumbnail_size = 'image-video';   
the_post_thumbnail( $thumbnail_size );

You could also use a switch instead of an if/else; either way, it's more efficient to use the get_post_format() method, above.

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I'm trying out both of your methods right now. Quick question though. What exactly is going on here -> $post_format = ( get_post_format() ? get_post_format() : 'standard' ); ... Specifically the ... get_post_format() ? get_post_format() – Colton Allen Mar 9 '12 at 2:35
I got it to work. Thanks for your help! Still curious about the "?" between the two get_post_format's – Colton Allen Mar 9 '12 at 2:45
@pope: it's called Ternary Operation, it's essentially a shorthand way of writing an if/then/else. In this case, IF there's a post format (?) THEN return the format to the variable, otherwise (ELSE :) return the string 'standard'. So the syntax is basically (condition) ? true : else – Evan Mattson Mar 9 '12 at 5:17
@EvanMattson nailed it. :) Here are the PHP.net docs for the ternary operator. – Chip Bennett Mar 9 '12 at 13:49
@EvanMattson Thanks so much to the both of you. I learned a lot! – Colton Allen Mar 9 '12 at 18:23

Your comments on the question lead me to believe that you are having trouble outputting the content correctly. You said you're echoing the output; try to return it instead:

if ( has_post_format( 'video' )) {
  $content = 'this is the video format';
return $content;

This may work if your content from this script is being output "before" the main post output, but instead you want it "inside" the main post output.

See append_content help for further discussion which might be helpful.

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