put calculated value in byline

Mike
Firstly I would like to thank you for all the time you spend answering queations and supporting people like me! I do still need a bit more help though please.

I have set up the query to select those posts where the meta key birthday value is current day and call the-wp-tiles to display a grid of those with a birthday today. (code in my customised content.php is here).
`<?php $query = new WP_Query( array(
‘meta_key’ => ‘birthday’,
‘meta_value’ => date( ‘F d’ )
));
$opts = array(
‘byline_template’ => “%title%”,
‘byline_template_textonly’ => false,
‘byline_opacity’ => ‘0.6’,
‘byline_color’ => ‘#000000’,
‘byline_height’ => 30,
‘byline_height_auto’ => false,
‘text_color’ => false,
‘image_text_color’ => ‘#FFFF99’,
‘ image_size’ => ‘original’,
‘post_type’=>’post’,
‘orderby’=>’title’,
‘order’=>’ASC’,
‘posts_per_page’=>’auto’,
‘ pagination’ => none,
‘category’=>’join’,
‘extra_classes’=> array(my-custom-styled-tiles),
‘post_status’=>’publish’); ?>
<?php the_content(); ?>
</div><!– .entry-content –>
<?php the_wp_tiles( $query, $opts); ?>
<?php wp_reset_postdata(); ?>`

On this particular page where I use the-wp-tiles query I am only selecting those whose birthday it is and would like to say on these bylines how old they are (or even just in a caption to go under the tile??). I don’t want it on any other page that the same tiles appear in various groupings but will just print the age variable on the text on some posts.
I store the birthdate as a post tag in the format ‘d-m-Y’ (eg 22-03-1996). I have tried to create a function in functions.php to calculate the age in years for example but seem to have problems getting it to read the tag ‘birthdate’ from the post as a variable:

function get_age( $birthdate )
{
        list($day, $month, $year) = explode( "-", $birthdate);

    // Find the differences
    $y_diff = date( "Y" ) - $year;
    $m_diff = date( "m" ) - $month;
    $d_diff = date( "d" ) - $day;

    // check if another year has been reached
    if ( $d_diff < 0 || $m_diff < 0 )
      $y_diff --;
    return $y_diff;

So firstly this function code to calculate the age isn’t working (something wrong with my code) it won’t seem to pick up my tag field variable $birthdate.
Secondly when I manage to get this bit of coding correct I need to pass this info to the-wp-tiles query so that for each post it returns (whose birthday it is today) it also returns the age and puts it onto the byline or as a tile caption.

Would appreciate any help you can offer.

Mike

I have returned to this – which I think is what you originally suggested – the wp byline template part is fine and prints an age correctly I just think my problem is still getting the variable $birthdate to be used correctly – it doesn’t like it – if I hard code $birthdate as YYYY-MM-DD into list($year, $month, $day) = explode( "-", '1998-03-26');it works fine for that one example but I can’t get it to read the variable being passed through – or at least it maybe passing it but the strtotime function returns 0 (and therefore this example has an age of 2015) .. it is probably something fundamental but is my call function my_age_function ( $birthdate ) correct ?- if have a tag on the post eg 1998-03-26 ?

function my_age_function( $birthdate )
{
    // Explode the date into meaningful variables
    list($year, $month, $day) = explode( "-", strtotime('$birthdate'));

    // Find the differences
    $y_diff = date( "Y" ) - $year;
    $m_diff = date( "m" ) - $month;
    $d_diff = date( "d" ) - $day;

    // If the day has not occured this year
    if ( $d_diff < 0 || $m_diff < 0 )
      $y_diff --;

    return $y_diff;
}

add_filter( 'wp_tiles_byline_tags', function( $y_diff, $post ) {
    $y_diff['age'] = my_age_function( $post );
    return $y_diff;
}, 10, 2 );