WordPress Post featured image URL in the header

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I want to add the featured image URL of a post to the header. When a Facebook user shares a WordPress page, this code in the header:

The rel="image_src" attribute is what facebook is searching for.

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<link rel="image_src" href="FEATUREDIMAGEURL">

Will return a specific image for the share. However, I cannot figure out how to add the URL of the post’s featured image… Can you?

I tried this: 

<?php if (has_post_thumbnail( $post->ID ) ): ?>
<?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ); ?>
<link rel="image_src" href="<?php echo $image; ?>">
<?php endif; ?>

But it gave me a Parse error: syntax error, unexpected ';' error.

Post Views: 2

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2 comments

  1. To answer this one and point to the real problem:

    As the <head> HTML tag comes far before the actual loop, you’ll need something else than the global $post.

    get_queried_object();
get_queried_object_id();

    The plugin

    The code is tested and works.

    As you might want to keep this functionality when switching themes, I’d suggest wrapping it up in a plugin.

    So the actual plugin should be something around the following lines:

    <?php
/** Plugin Name: (#70215) »kaiser« Post Thumbnail image for FB */
function wpse70215_fb_img()
{
    // Not on a single page or post? Stop here.
    if ( ! is_singular() )
        return;

    $post_ID = get_queried_object_id();

    // We got no thumbnail? Stop here.
    if ( ! has_post_thumbnail( $post_ID ) )
        return;

    // Get the Attachment ID
    $att_ID = get_post_thumbnail_id( $post_ID );

    // Get the Attachment
    $att    = wp_get_attachment_image_src( $att_ID );

    printf(
         '<link rel="image_src" href="%s">'
        ,array_shift( $att )
    );
}
add_action( 'wp_head', 'wpse70215_fb_img' );

  2. there was a closing bracket missing in the second line; and you need to reference the first array element of $image:

    <?php if (has_post_thumbnail( $post->ID ) ): ?> 
<?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ) ); ?> 
<link rel="image_src" href="<?php echo $image[0]; ?>"> 
<?php endif; ?>

    http://codex.wordpress.org/Function_Reference/wp_get_attachment_image_src

    you might also want to add a check for single post or page, to avoid any unwanted output in index or archive pages; example:

    <?php if ( has_post_thumbnail( $post->ID ) && is_singular() ): ?>