WordPress: Overwrite the canonical URL in YoastSEO
If you don't pass any priority to the action wordpress will take it as 10. Yoast SEO also call this filter to add canonical url so wordpress executed function in the order in which they were added to the action.
So change this line
add_filter( 'wpseo_canonical', 'prefix_filter_canonical_example' );With this
add_filter( 'wpseo_canonical', 'prefix_filter_canonical_example', 20 );