Displaying ACF field in page or archive head - php

Question

I would like to use an ACF field to inject Schema merkup to a few specific pages on my WordPress website. Some of them are custom taxonomies or custom post types.
After a two hour research on the topic, I am still stuck.
I have created a text area field called schema_code and entered the desired Schema markup for some of my sub pages.
I currently use this code in my functions.php which does not do anything:
function acf_header_script() {
$schema = get_field('schema_code');
echo '<script type=application/ld+json>' . json_encode($schema_code) . '</script>';
}
add_action ( 'wp_head', 'acf_header_script' );
What am I missing here? Thanks a lot!

Answer 1

The second parameter of the ACF get_field() is required in this case, since you're not in the loop. It is either the post->ID or it's the taxonomy ID where it's {taxonomy_name}_{taxonomy_id} https://www.advancedcustomfields.com/resources/get_field/
Since you want to do this on pages and archives, etc... You need to first determine if it's a single page or an archive, etc.
function acf_header_script() {
// is it a single post?
if ( ! is_single() ) {
// no? get the queried object.
$object = get_queried_object();
if ( is_a( $object, 'WP_POST' ) ) {
$param = $object->ID;
} else {
$param = $object->taxonomy . '_' . $object->term_id;
}
} else {
// yes it's a single.
global $post;
$param = $post->ID;
}
$schema = get_field( 'schema_code', $param );
// if $schema is not empty.
if ( $schema ) {
echo '<script type=application/ld+json>' . json_encode( $schema ) . '</script>';
}
}
add_action( 'wp_head', 'acf_header_script' );