Just updated another Wordpress site from PHP 7.4 to 8.1 and needed to update the deprecated create_function. Here's the old code:
add_filter( 'loop_shop_per_page', create_function( '$cols', 'return '.$sp_products_per_page.';' ), 20 );
I updated it to:
add_filter( 'loop_shop_per_page', function($cols) { return $sp_products_per_page; }, 20);
But it still doesn't seem to be working correctly. Is this syntax correct?
From the two functions you have, I assume it's a scope issue.
$sp_products_per_page is declared/exists on a global scope, and because you use an anonymous function, it's not accessible from the function scope.
So instead of
add_filter( 'loop_shop_per_page', function($cols) { return $sp_products_per_page; }, 20);
You'll need to add a use keyword
add_filter( 'loop_shop_per_page', function($cols) use ($sp_products_per_page) { return $sp_products_per_page; }, 20);
A bit of formatting and we have this
add_filter( 'loop_shop_per_page', function($cols) use ($sp_products_per_page) {
return $sp_products_per_page;
}, 20);
