While adding some features to Templ33t, I ran into a situation where I need certain custom fields to be searchable. I didn’t want to add any extra input fields to the search box (wouldn’t make sense in this context)Â or hack apart the query with a bunch of joins and conditions. A fair amount of searching through the codex and google yielded few results. After tinkering for a while, I came up with a simple (if hack-ish) solution.
Using the content_save_pre filter, I was able to append an identifiable HTML comment containing the custom field text to the page content. This makes the custom field text searchable as it is now, for all intents and purposes, part of the main content. It also allows you to be selective about which custom fields are included. The tag is then stripped before editing the page/post using the the_editor_content filter. Here is the code.
// add filter callbacks
add_filter('content_save_pre', 'myplugin_add_comment', 10);
add_filter('the_editor_content', 'myplugin_strip_comment', 1);
/**
* Append custom field content to main content in comment form for searchability.
* @param string $content
* @return string
*/
function myplugin_add_comment($content = null) {
if(array_key_exists('meta', $_POST) && !empty($_POST['meta'])) {
$cfields = array('mycustom_text', 'mycustom_other', 'mycustom_etc');
$append = '';
$content .= ' '.$append;
}
return $content;
}
/**
* Remove custom field comment from end of content before editing.
* @param string $content
* @return string
*/
function myplugin_strip_comment($content = null) {
$content = preg_replace('/()/mi', '', $content);
return $content;
}
This worked rather well for me but I realized that the matched text would not show up in the search results. This isn’t too big a deal if you’re not using  any keyword highlighting or similar functionality. In order to support those scenarios though, I modified the structure of the comment and attached a callback to the the_content filter which renders the comment as appended text to the post for search results (or strips it in any other context). Here is the new code.
// add filter callbacks
add_filter('content_save_pre', 'myplugin_add_comment', 10);
add_filter('the_editor_content', 'myplugin_strip_comment', 1);
add_filter('the_content', 'myplugin_content_filter', 1);
/**
* Append custom field content to main content in comment form for searchability.
* @param string $content
* @return string
*/
function myplugin_add_comment($content = null) {
if(array_key_exists('meta', $_POST) && !empty($_POST['meta'])) {
$cfields = array('mycustom_text', 'mycustom_other', 'mycustom_etc');
$append = '';
$content .= ' '.$append;
}
}
/**
* Remove custom field comment from end of content before editing.
* @param string $content
* @return string
*/
function myplugin_strip_comment($content = null) {
$content = preg_replace('/()/mi', '', $content);
return $content;
}
/**
* Transform custom fields comment into appended text for search results
* @param string $content
* @return string
*/
function myplugin_content_filter($content = null) {
if(is_search()) {
$content = preg_replace('/(::[A-Z0-9\_\-]+::)/i', ' ... ', preg_replace('/()/mi', '$2', $content));
} elseif(is_page()) {
$content = myplugin_strip_comment($content);
}
return $content;
}
I know this is not the most ideal or efficient solution, but it does work. I hope it helps!