Home » Wordpress » The Ultimate WordPress Thumbnail Hack

Ok, so there are a number of hacks out there that help you fetch a thumbnail to go with your post summary, via different methods. Here is one hack I created that uses all the best sources I’ve found fused into one.

Our final script will follow the following process in this order:

1. Check if Post Thumbnail has been set (a specific feature for setting thumbnails only available in WordPress 2.9 and above). If it is set use that as the post thumbnail.
2. Check if a custom field has been set with the key ‘thumbnail’ and the URL of the image as its value. If it is set use that for a thumbnail.
3. Check if any images are found in the post and if yes, use the first one found as the thumbnail.
4. If none of the above conditions were satisfied, display a default thumbnail.

The script also provides for resizing of images via the timthumb.php script (see instructions for downloading that below).

NOTE: I am having problems displaying code here on the blog post using WP Syntax, so until I sort that out it is better to download the code from these links:

Code for functions.php

Code to go in your template file (probably index.php)

So, let’s get cracking. First off you have to open your functions.php file (found with the rest of your template files) and insert the following code:

< ?php
// see if there is any image in the posts_nav_link
function findImage() {
	$content = get_the_content();
	$count = substr_count($content, ' 0) return true;
	else return false;
}

// retreives image from the post
function getImage($num) {
	global $more;
	$more = 1;

	$content = get_the_content();
	$count = substr_count($content, '');
		$postOutput = substr($post, 0, $imgEnd+1);
		$image[$i] = $postOutput;
		$start=$imgEnd+1;
		$cleanF = strpos($image[$num],'src="')+5;
		$cleanB = strpos($image[$num],'"',$cleanF)-$cleanF;
		$imgThumb = substr($image[$num],$cleanF,$cleanB);
	}

	if(stristr($image[$num],'

Then in your template file you need to insert this other code:

< ?php
	$postimageurl = get_post_meta($post->ID, 'thumbnail', true);

	/* Check if Post Thumbnail has been set (WordPress 2.9 and above) */
	if ( (function_exists('has_post_image')) && (has_post_image()) )
	{ ?>


< ?php echo (the_post_image('thumbnail')); ?>


	< ?php } 																	

	/* Check if custom field URL is set */
	else if ($postimageurl) { ?>





	< ?php } 

	/* Check if any images found in post and display the first one found */
	else if  ((function_exists('getImage')) && (function_exists('getImage')) && (findImage())) { ?>





	< ?php } 

	/* Display default image */
	else { ?>





	< ?php } ?>

You can set the size of the images in the script (I am using 115px by 115px).

For this to work you also need to download the timthumb.php script from here

Just put the timthumb.php file together with your theme’s files.

If you have any advice for optimising this code do let me know, as I am by no means an expert PHP coder.

Related posts:

1. Using the Post Thumbnail feature in WordPress
2. Using the NextGen Gallery for WordPress
3. Rotating Images in WordPress
4. PHP Notes – POST Vs. GET
5. Use WordPress functions outside of WordPress