PHP snippet showing in footer

Hello,

I’ve got a PHP snippet only running in the backend, but for some reason the snippet is displaying right at the bottom of the site in the footer.

It is priority 1 and the only snippet on the site.

Snippet is as follows if that makes a difference:

function remove_h1_from_heading($args) {
// Omit h1, h4, h5, pre from the list
$args['block_formats'] = 'Paragraph=p;Heading 2=h2;Heading 3=h3;Heading 4=h4';
return $args;
}
add_filter('tiny_mce_before_init', 'remove_h1_from_heading' );

Can you please let me know if I’ve done anything wrong, and if so, what I can do to remedy?

Kind regards,
Jamie

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