Is there a hook in WordPress that I can use to filter the output of a specific shortcode? Something like this:
add_filter('shortcode_output', 'my_filter_function', 2);
function my_filter_function ( $output, $shortcode ) {
....
}
Where $shortcode would be something like [my_schortcode] or even better, shortcode and its attributes separated into an array.
There is no filter that I know of that is meant to target individual shortcodes like you want.
You can filter attributes with shortcode_atts_{$shortcode} though.
You can hijack another shortcode by creating your own callback and registering it with the original shortcode slug. I think that is what you are probably going to need to do.
Proof of concept:
function my_gallery_shortcode($atts) {
return 'howdy';
}
add_shortcode('gallery','my_gallery_shortcode');
Now try to use a gallery :)
the_content. It works for my use-case.
WordPress 4.7 introduced a new filter, do_shortcode_tag, to do exactly this.
function example_shortcode_output($output, $tag, $attr, $m){ if($tag == 'gallery') $output = str_replace("\t", '', $output); return $output; } add_filter('do_shortcode_tag', 'example_shortcode_output', 10, 4);
While there is no hook, there is a small workaround that makes your end-goal possible. You can create a new shortcode that, on a per-instance basis, you always wrap around any other shortcode whose output you want to filter.
Usage in a post, etc:
Here is some post text. Blah blah...
[filter][target_annoying_shortcode size="small" limit="20"][/filter]
Here is some more text in my post. More blah blah...
In functions.php:
function my_shortcode_output_filter( $attr, $content ) {
// Express the shortcode into its output
$content_translated = do_shortcode(trim($content));
if($shortcode_to_modify == $content || !$content_translated) {
// Error handling
return 'There was an error in filtering shortcode: '.$content;
}
// Now modify the output as you like, here...
$content_translated_and_filtered = $content_translated;
return $content_translated_and_filtered;
}
add_shortcode('filter', 'my_shortcode_output_filter');
The only thing that you can filter is the attributes fo the shortcode:
apply_filters( "shortcode_atts_{$shortcode}", $out, $pairs, $atts );
Point is, that $shortcode is the third argument when registering a shortcode. This argument is pretty new and nearly no shortcode uses it, therefore it will fall back to the default - which is a string of ''.
This leads to a funny result:
add_filter( 'shortcode_atts_', 'wpse112294_shortcode_atts_cb' );
function wpse112294_shortcode_atts_cb( $out, $pairs, $atts )
{
// here we need to find a way to uniquely identify a shortcode
// for which we ain't got a name
// something that makes the shortcode unique:
$found = isset( $pairs['foo_attribute_key'] );
if ( $found )
{
// Instantly remove this filter to save processing time:
remove_filter( current_filter(), __FUNCTION__ );
// do something stunning in here!
}
return $out;
}
So, yes, with a 90% chance we need to filter the output of every(!) shortcode and try to somehow identify the shortcode by either some default arguments ($pairs) or by input arguments (impossible). Then, finally we're able to process the output. Are we able to process the string itself? No. This has to be done the way @s_ha_dum showed above.
While @s_ha_dum gave a decent answer, you can create a new shortcode for the purpose of filtering an existing shortcode. For example,
function filter_function($atts, $content) {
extract(shortcode_atts(array(
'att1' => 'val1',
'att2' => 'val2'
), $atts));
//save shortcode output in $return
$return = do_shortcode("[existing_shortcode att1='$att1' att2='$att2'".$content."/existing_shortcode]");
//insert code to modify $return
echo $return;
}
add_shortcode('new_shortcode','filter_function');
note that for the [embed] shortcode, you have to use
global $wp_embed;
$return = $wp_embed->run_shortcode("[embed ...
instead of do_shortcode
