How to selected which tags to print, instead of printing the whole tag list?

Question

When having this:

$tag_list = get_the_tag_list( '', ', ' );

I substituted the meta print:

printf(
$tag_list,
$category:list,
etc
);

by this:

$printArray_tag_list = explode(', ', $tag_list);
echo $category_list."/".$printArray_tag_list[0].','.$printArray_tag_list[1];

to print only the first two tags from the list (the first tags inserted in the post editor). Only then I realized that they are alphabetically ordered and those are not the tags I want to print.

Is there a way to print selected tags? Maybe selecting them in the custom fields?

Answer 1

By get_the_tags() you receive an array of tags attached to the current post. So you could do the following:

$tags = get_the_tags();
$tag_ids_to_print = array( 1, 2, 3 ); //List of Tag IDs which you want to be printed

$print_tags = array();
if( is_array( $tags ) ){
    foreach( $tags as $tag ){
        if( in_array( $tag->term_id, $tag_ids_to_print ) )
            $print_tags[] = $tag;
    }
}

$tag_list = '';
if( count( $print_tags ) > 0 ){
    //Execute only, when tags found
    $i = 0;
    foreach( $print_tags as $tag ){
        if( $i == 1 ) $tag_list .= ', ';
        $tag_list .= '<a href="' . get_tag_link( $tag->term_id ) . '">' . $tag->name . '</a>';
        $i = 1;
    }
}

Docs:

https://codex.wordpress.org/Function_Reference/get_the_tags

Answer 2

Custom Field Tag filter:

You can try the following code snippet to filter tags from a custom field:

/**
 * Support the 'include_tags' custom field (comma seperated tag slugs) 
 * to filter out those tags to display.
 *
 * @see http://wordpress.stackexchange.com/a/183929/26350
 */

! is_admin() && add_filter( 'get_the_terms', function( $terms, $post_id, $taxonomy )
{
    if(    'post_tag' === $taxonomy 
        && ! empty( $terms ) 
        && $include = get_post_meta( $post_id, 'include_tags', true ) 
    ){      
        // We only want lower case and trimmed strings from the custom meta field:
        $include_tags = array_map( 'trim', array_map( 'strtolower', explode( ',', $include ) ) );

        // Let's filter out the terms to display:
        if( ! empty( $include_tags ) )
            $terms = array_filter( $terms, function( $t ) use ( $include_tags ) {               
                return in_array( $t->slug, $include_tags );
            });
    }
    return $terms;
}, 10, 3 );

For example if you use the_tags() in your template and have the following tags in a given post:

then you can add the custom field include_tags with a comma seperated list of tags you want to filter out:

Then it will show like this on your front end:

Similarly we could support exclude_tags filtering with:

return ! in_array( $t->slug, $include_tags );

instead.