Passing variable from child theme to parent theme

Question

I want to pass my google map custom colors from my child theme to my parent theme.

So in my Parent Theme's functions.php I have

add_filter( 'post_thumbnail_html', "map_thumbnail" );
function map_thumbnail($html, $color1, $color2) {
       $my_post = get_post($post->ID);
       $water_color=$color1;
       $tree_color=$color2;
       if($my_post->post_name == "contact") {
       $html = '<img height="100%" width="100%" src="http://maps.googleapis.com/maps/api/staticmap?watercolor='.$water_color.'treecolor='.$tree_color.'">';
       }
return $html;
}

I just want to pass two colors from my child theme's functions.php like so,

$color1 = '#fb0000';
$color2 = '#c0e8e8';
apply_filters('post_thumbnail_html', $color1, $color2);

But unfortunately this is not working. Can anyone help me out here ? I have 3 child themes and all of them have the same map, just the tree color and water color are different. I want to keep the main map_thumbnail function in the parent theme and pass only the individual colors from my child themes. Please help me out if possible.

Answer 1

Stick to filtering one value at a time to keep it simple, and add filters for the colors to be used by the child theme:

add_filter( 'post_thumbnail_html', 'map_thumbnail');
function map_thumbnail($html) {
   $my_post = get_post($post->ID);
   $defaultcolor1 = "#??????"; // parent theme default
   $defaultcolor2 = "#??????"; // parent theme default
   $water_color = apply_filters('water_color',$defaultcolor1);
   $tree_color = apply_filters('tree_color',$defaultcolor2);
   if($my_post->post_name == "contact") {
       $html = '<img height="100%" width="100%" src="http://maps.googleapis.com/maps/api/staticmap?watercolor='.$water_color.'treecolor='.$tree_color.'">';  
   }
   return $html;
}

So in the child theme you can use:

add_filter('water_color','custom_water_color');
add_filter('tree_color','custom_tree_color');

function custom_water_color() {return '#fb0000';}
function custom_tree_color() {return '#c0e8e8';}

Answer 2

Without having tried it myself I would suggest you write a small function for your child theme and then call the parent's theme funstion like this:

add_filter( 'post_thumbnail_html', "child_map_thumbnail", 11 );

function child_map_thumbnail($html) {

    $color1 = '#fb0000';
    $color2 = '#c0e8e8';

    map_thumbnail($html, $color1, $color2);

    return $html;

}

As I said: I haven't tried this myself – but I suppose the function of your parent theme should be available – so basically my suggestion would be to call that function instead of passing variables…